weight loss journey intermittent fasting

'I Started A 16:8 Intermittent Fasting Schedule And Walking For Weight Loss To Lose 102 Pounds'

"I was too strict with my diet before, and it always backfired."

I had always struggled with weight issues, even as a kid. I had tried every diet trend out there, and I had personal trainers as well. When I tried to lose weight, I couldn't maintain it and I'd quickly gain it back, or I would plateau and give up. In 2018, I lost 40 pounds, only to gain it all back in 2019.

I knew I needed to make a permanent change when a family member asked my mom if I was expecting at my niece’s birthday party in June 2019. (I was not.) Rather, I was depressed and bloated. I had put on 30 pounds in 3 months. Mentally, I was struggling and trying to hide behind black clothes. I wasn’t myself. I was taking naps every day at lunch. And anytime I was with my boyfriend, we were eating. I was barely moving.

So when I heard what was asked about me at my niece’s birthday party, I started changing my eating habits the next day.

I had heard about intermittent fasting and I decided to try it. I wanted to do something different than I had done before.

I started a 16:8 eating plan . I also try not to eat in the window two hours before bed .

When I tried to lose weight before, I had always been too strict and cut out "bad" foods for months. So when I would start trying to ease those "bad" foods back into my life, I would end up gaining my weight back. Intermittent fasting has been working for me, and I now allow myself to have cheat days for my food cravings.

Here’s what I eat in a day now.

• Breakfast: When I'm not fasting, I may make a protein shake (vanilla protein powder , unsweetened vanilla almond milk, banana, powdered peanut butter, and honey), or a veggie omelet, or steel-cut oatmeal (cinnamon, sweetener, and chopped almonds mixed with unsweetened vanilla almond milk).
• Lunch: Flatbread pizza (turkey pepperoni, Impossible burger , mushrooms, green peppers, and onions on a 130-calorie flatbread) or a grilled chicken and veggie wrap with sweet potato fries.
• Snacks: Deli turkey, cheese, almonds, grapes, or a protein bar .
• Dinner: Taco salad (sautéed chicken, onions, and green peppers topped with crumbled cotija cheese, pico de gallo, and guacamole on a bed of lettuce); baked salmon, steamed broccoli, and a baked sweet potato; or spaghetti squash with a salad.
• Dessert: Smart Sweets gummy bears, Halo Top ice cream, grapes or a fruit smoothie.

I started exercising at the beginning of my weight-loss journey.

My old apartment complex had a walking trail, so I would go outside and walk for 30 minutes before work. That first week, I walked three days, and the next week I walked five days.

I also stopped taking naps at lunch. Some days I would walk on my lunch break as well. I found myself enjoying the walks. My apartment complex also had a gym. Eventually, I started jogging for 30 minutes, and started going into the gym to do some strength training .

Now I exercise every day. I still love walks and jogs. When I go to the gym, I do mostly strength training. Some days I get on the elliptical or stair machine. I purchased resistance bands , kettlebells , dumbbells, a jump rope, a mini stepper, a yoga ball, and ankle weights when the pandemic first hit to continue exercising at home. I also like doing HIIT or hip-hop dance videos on Youtube. I track my activity daily with my Apple Watch . I try to close my rings every day and beat my monthly challenge.

These three changes made the biggest difference in my weight-loss results.

• I put myself on a schedule. I wake up at 4 a.m. every day to exercise and try to be in bed by 9 pm. I’m no longer taking naps at lunch as well.
• I drink tons of water. I drink more water to stay hydrated and to help me stay full. Instead of sodas, I have sparkling water instead.
• I always have my fitness tracker on. If I am not sleeping, I am wearing my fitness tracker. I try to get at least 10,000 steps in each day .

Since June 2019, I’ve lost 102 pounds. Now I am in the process of toning.

Changing my mindset about having a healthier lifestyle has helped my weight-loss journey. I told myself I was going to lose weight, and I did—but I didn’t think of the eating changes I made as a diet. Diets are temporary—lifestyle changes last forever.

Speak it into existence. If you have a negative mindset towards changing your lifestyle, you’re not going to want to do it and you probably won’t make the changes. I've realized that self-discipline is the highest form of love I can give myself. Find what works best for you.

If you do not have access to a gym, find workouts on Instagram , Pinterest, YouTube, TikTok, etc. I do not need to have a gym to exercise. Lastly, have patience because it is going to take time. I am happy I started my weight loss journey. My body feels so much lighter, I feel younger, and have a lot more energy.

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Benefits of Different Intermittent Fasting Schedules

• Why to Start Fasting
• Time-Restricted IF
• Overnight IF
• Alternate Day IF
• 5:2 Intermittent Fasting
• Warrior Diet (20:4)
• One Meal a Day
• Eat Stop Eat
• Other Benefits

Intermittent fasting (IF) is a way of eating that involves periods of fasting alternating with eating windows. Different methods of IF vary in fasting/eating periods and restrictions on what you are allowed to eat and drink.

IF is often used for weight loss and preventing or managing some chronic diseases. Fasting is also used for non-diet reasons, such as religious beliefs and traditions.

This article reviews reasons for following an intermittent fasting eating pattern, different methods of IF, and the health benefits and safety concerns of IF.

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Why Do People Start Intermittent Fasting?

People choose to start IF for various reasons. Aside from fasting for religious beliefs or cultural reasons, the most common health-related reason for fasting is for weight loss.

A randomized controlled trial involving people with prediabetes (the stage before type 2 diabetes ) who were overweight or had obesity divided them into one of two intermittent fasting methods or a control group.

At the end of the trial, both fasting groups had greater reductions in body weight, body mass index (BMI) , and waist circumference compared to the control group.

BMI is a dated, flawed measure. It does not take into account factors such as body composition , ethnicity, sex, race, and age. Even though it is a biased measure , BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

A systematic review of 40 studies on IF found that it helped people lose weight, with a usual weight loss of 7 to 11 pounds over 10 weeks.

Other reasons may include helping prevent or manage some chronic medical conditions, enhancing physical performance, or helping improve thinking and memory.

Intermittent Fasting vs. Fasting Before Bloodwork

Intermittent fasting is different from fasting for blood work . Some blood work tests require you to fast for at least 8 hours or overnight before having your blood drawn. This is done so the test can be as accurate as possible. Fasting for blood work is only done when instructed by a healthcare provider before certain labs are drawn.

There are several different methods of IF, but all involve periods of fasting or modified fasting. Fasting windows may range from 10 to 36 hours, depending on the method. In some types of IF, you cannot eat any food in a fasting period, while others are modified fasts, allowing for around 500 to 600 calories of food and/or beverages.

Continue reading to learn about seven different methods of intermittent fasting.

1. Time-Restricted (16:8 or 14:10) Intermittent Fasting 

Time-restricted fasting is one of the most commonly used methods of IF, especially for beginners. This method follows a 16:8 or 14:10 schedule, in which you fast for 16 or 14 hours a day and have an 8- or 10-hour eating window, respectively.

• Schedule : There are no restrictions on when you need to have your fasting hours begin or end. However, it is important to be consistent with what you choose. Most people have the majority of their fasting hours overnight. An example might be to fast from 6 p.m. to 10 a.m. for a 16:8 schedule or 7 p.m. to 9 a.m. for a 14:8 schedule. 
• Rules : Finish your meal before your eating window ends. Water and other no-calorie beverages, such as herbal tea and black coffee, are allowed during the fasting window.

2. Overnight (12:12) Intermittent Fasting

A shortened version of time-restricted fasting is to fast overnight for 12 hours. This method of IF might be a good option for beginners, as most of the fasting window is while you’re sleeping.

• Schedule : Choose a 12-hour overnight fasting period—for example, 8 p.m. to 8 a.m.
• Rules : Finish your meal before your eating window ends in the evening. Water and other no-calorie beverages, such as herbal tea and black coffee, are allowed during the fasting window.

3. Alternate Day Intermittent Fasting

Sometimes referred to as the 4:3 IF method, alternate day fasting involves fasting every other day. Being a more extreme method, this variation of IF may not be appropriate for beginners or people with certain medical conditions.

• Schedule : Fast for a full day, followed by a day of eating regularly. Continue alternating between fasting and eating days. Some variations include fasting past 24 hours and up to 36 hours, then eating for 12 hours.
• Rules : This method has a couple of variations. One is to fast (go without food completely) on your fasting day. Another is to eat minimally, or around 500 calories on your fasting day. Water and other no-calorie beverages, such as unsweetened tea and black coffee, are allowed on the fasting day.

4. 5:2 Intermittent Fasting

The 5:2 diet, also known as the Fast Diet, involves eating regularly five days a week and following a modified fast two days. This method is a little more flexible, as you are allowed to choose which days of the week are your modified fasting days.

• Schedule : During a seven-day week, choose two days to fast. It’s best to break up fasting days so as not to be consecutive. The remaining five days are regular eating days.
• Rules : On your fasting days, you may eat minimally, around 500 to 600 calories per day. On eating days, eat a normal day's worth of calories—but don’t overeat to compensate for the fasting days. Water and other no-calorie beverages, such as unsweetened tea and black coffee, are allowed on the fasting days.

5. Warrior Diet (20:4) Intermittent Fasting

A more drastic variation of IF, the warrior diet involves eating minimally (usually raw fruits and vegetables) during the day, followed by eating one large meal at night within a four-hour period.

• Schedule : Twenty hours of eating very little is followed by a four-hour window in which you are allowed to eat the remaining calories for the day.
• Rules : During the 20-hour modified fast, you may consume some raw fruits and vegetables, small amounts of protein, and beverages such as milk, water, coffee, and unsweetened tea. During the four-hour eating window, you may eat however much and whatever you want, but are encouraged to eat nutrient-dense foods.

6. One Meal a Day (OMAD) Intermittent Fasting

One of the most extreme methods of IF, the OMAD diet . is a 23-hour fast followed by a 1-hour eating window in which you eat the entire daily calories. This fasting method may not be appropriate for beginners or people with certain medical conditions.

• Schedule : Fasting for 23 hours, followed by 1 hour of eating a very large meal. The 1-hour eating window should be within the same 4-hour time frame each day.
• Rules : You are encouraged to eat as many calories as you normally would during a day in your 1-hour eating window. There are no restrictions on the types or amount of food you can eat. During the 23-hour fasting period, no- or very-low-calorie beverages are allowed, such as water, unsweetened tea, and black coffee.

7. Eat Stop Eat Intermittent Fasting

The Eat Stop Eat method of IF involves fasting for 24 hours one or two nonconsecutive days a week. This method is similar to the 5:2 fasting diet. However, the 5:2 method allows for 500 to 600 calories on fasting days, while the Eat Stop Eat method does not.

• Schedule : Eat normally for at least one day, then stop eating (fast) for a full 24 hours (i.e., 5 p.m. until 5 p.m. the next day). Resume eating normally again for one or more days. You may choose one or two days of fasting during the week, spaced with at least one normal day of eating in between.
• Rules : No food is allowed during the fasting period. However, water, unsweetened tea, and coffee are allowed. There are no restrictions on what or how much you eat on non-fasting days.

Besides Weight Loss, Does Intermittent Fasting Have Other Benefits?

Some studies have shown promising results for health benefits of IF beyond weight loss. The same randomized controlled trial mentioned previously that showed IF beneficial for weight loss also found the two intermittent fasting groups to have significant decreases in both blood glucose (sugar) and triglyceride (a type of fat) levels.

A different randomized controlled trial looked at the effects of a 5:2 fasting diet in people with metabolic syndrome (a group of symptoms occurring together that increase the risk of type 2 diabetes, stroke , and cardiovascular disease),

Over eight weeks, they found that the fasting group improved certain cardiometabolic risk factors, including reducing fat mass, oxidative stress (an imbalance between free radicals and antioxidants in your body), and inflammation.

In addition, IF significantly altered the gut microbiota (the collection of bacteria and other organisms in the gastrointestinal tract), improving overall gut health and carbohydrate metabolism.

Some studies have shown beneficial effects of IF on physical activity performance, including studies done on elite cyclists, generally healthy active women and men. However, one small study showed a negative impact on sprinting performance in males.

Some studies concluded that IF may improve memory and brain health. Other research has shown that IF may result in improved metabolism.

Additional, larger clinical trials and research is needed to determine whether IF is beneficial in other ways and in the long term.

What Is Metabolism?

Metabolism is a term that refers to all of the chemical processes or changes that occur in the body at the cellular level. These changes make energy and the materials organisms and cells need in order to grow, reproduce, and maintain life. 

In relation to diet, metabolism is the process of digesting or breaking down the food you eat into a simpler form the body is able to use. Metabolism is also involved when your body breaks down muscle or stored fat to be used as energy during periods of strenuous exercise or fasting.

Safety of Intermittent Fasting: Who Shouldn’t Try It

While IF may be beneficial for someone trying to lose weight, it isn’t for everyone. Always talk with a healthcare provider before starting a new diet or eating pattern, especially if you have a known medical condition.

IF may be unsafe for people with diabetes who take insulin or other glucose-lowering medications and people who are on medication that needs to be taken with food. Individuals with a history of disordered eating, children under 18, and people who are pregnant or breastfeeding should not follow IF diets.

Possible Risks in Men vs. Women

A review of human trials found that fasting may reduce levels of androgens (reproductive and growth hormones), which can negatively impact metabolic health and libido (sexual desire) in males.

Some studies suggest that women may be more sensitive to fasting, most likely relating to fluctuating hormones. One small study concluded that IF may increase stress in women,

More research is needed to determine the different effects of IF on men versus women.

Intermittent fasting (IF) involves periods of fasting alternating with periods of eating. There are several methods of IF with variations in the amount of time spent fasting versus eating. Fasting for health is done for different reasons, including weight loss, disease prevention or management, and to help improve other aspects of health, such as physical performance, metabolism, and brain health.

People with diabetes who take insulin or other glucose-lowering medications and those who are on medication that needs to be taken with food should not follow IF eating patterns. Others who should also avoid IF include individuals with a history of disordered eating, children under 18, and pregnant or breastfeeding people. Talk with a healthcare provider if you are considering trying IF.

Chair SY, Cai H, Cao X, Qin Y, Cheng HY, Ng MT. Intermittent fasting in weight loss and cardiometabolic risk reduction: a randomized controlled trial . J Nurs Res . 2022;30(1):e185. doi:10.1097/jnr.0000000000000469

Seimon RV, Roekenes JA, Zibellini J, et al. Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials . Mol Cell Endocrinol . 2015;418 Pt 2:153-172. doi:10.1016/j.mce.2015.09.014

Guo Y, Luo S, Ye Y, Yin S, Fan J, Xia M. Intermittent fasting improves cardiometabolic risk factors and alters gut microbiota in metabolic syndrome patients . J Clin Endocrinol Metab . 2021;106(1):64-79. doi:10.1210/clinem/dgaa644

Moro T, Tinsley G, Longo G, et al. Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial . J Int Soc Sports Nutr . 2020;17(1):65. doi:10.1186/s12970-020-00396-z

Martínez-Rodríguez A, Rubio-Arias JA, García-De Frutos JM, Vicente-Martínez M, Gunnarsson TP. Effect of high-Intensity Interval training and Intermittent fasting on body composition and physical performance in active women . Int J Environ Res Public Health . 2021;18(12):6431. doi:10.3390/ijerph18126431

Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males . J Transl Med . 2016;14(1):290. doi:10.1186/s12967-016-1044-0

Cherif A, Meeusen R, Farooq A, et al. Three days of intermittent fasting: repeated-sprint performance decreased by vertical-stiffness impairment . Int J Sports Physiol Perform . 2017;12(3):287-294. doi:10.1123/ijspp.2016-0125

Seidler K, Barrow M. Intermittent fasting and cognitive performance - Targeting BDNF as potential strategy to optimise brain health . Front Neuroendocrinol . 2022;65:100971. doi:10.1016/j.yfrne.2021.100971

Vasim I, Majeed CN, DeBoer MD. Intermittent fasting and metabolic health . Nutrients . 2022;14(3):631. doi:10.3390/nu14030631

Cienfuegos S, Corapi S, Gabel K, et al. Effect of intermittent fasting on reproductive hormone levels in females and males: a review of human trials . Nutrients . 2022;14(11):2343. doi:10.3390/nu14112343

Solianik R, Sujeta A. Two-day fasting evokes stress, but does not affect mood, brain activity, cognitive, psychomotor, and motor performance in overweight women . Behav Brain Res . 2018;338:166-172. doi:10.1016/j.bbr.2017.10.028

By Brittany Poulson, MDA, RDN, CD, CDCES Poulson is a registered dietician and certified diabetes care and education specialist. She is based in Utah.

Evidence based

Key takeaways

Getting started: To begin, simply delay the time you eat breakfast. For example, if you usually eat breakfast at 7am, wait until 9 am. Then stretch it longer. Learn more

Who shouldn’t fast? Some individuals should avoid fasting or only fast under direct physician supervision. See our list. Learn more

Your complete guide to intermittent fasting

• Getting started
• How to succeed
• Precautions

Intermittent fasting has become one of  the most popular  and possibly easiest means for weight loss and better health. For some, fasting may sound scary and uncomfortable, but it doesn’t have to be. In this guide, you’ll learn all you need to know to get started with a successful intermittent fasting routine.

What is intermittent fasting?

Intermittent fasting, often abbreviated as IF, is any voluntary time period where you go without food. It is not a diet, per se, since it doesn’t specify what to eat; it only specifies when to eat.

You may be more likely to get better health benefits if you also pay attention to what kinds of foods you eat, but some studies involving IF that did not control what people ate still showed meaningful improvements.

One nonrandomized trial showed improved weight loss, blood sugar, and lipids with as little as 14 hours of daily fasting and no change in the participants’ baseline diet.  However, that may not mean people can eat whatever they want during the eating window. Many clinicians feel their patients have more success with intermittent fasting when eating  low-carb  or  higher protein  diets, but there is currently insufficient evidence that pairing one particular type of diet with IF is superior to another.

While the buzz surrounding IF is recent, this practice isn’t new. Religious cultures have practiced it for centuries.  And although accurate data are difficult to acquire, it is likely that hunter-gatherer societies and inhabitants of so-called Blue Zones have adjusted their meal frequency to one or two meals per day without snacks for generations.  Now, it’s our turn to catch on.

Because the definition of IF is often different depending on the source you consult, it helps to clarify what we mean when we say “intermittent fasting.”

At Diet Doctor, we use intermittent fasting as an umbrella term, which encompasses the following:

Time-restricted eating , which we define as any fast less than 24 hours

Short-term fasting , which we define as fasting between 24 and 36 hours

Alternate day fasting, which we define as eating one day and fasting the next

Longer-term fasting , which we define as any fast greater than 36 hours

This guide will focus on time-restricted eating and short-term fasts. For longer-term fasts see our guide here . For alternate day fasting, see our full-length guide here .

How to get started

Intermittent fasting doesn’t have to be difficult. In fact, it shouldn’t be difficult at all!

All you have to do is allow more time between your meals. This can be as simple as stopping dinner at 7pm and not eating anything until 7am. That is a 12-hour fast. While a 12-hour fast hasn’t been studied in experimental trials, it logically seems like the first place to start with time-restricted eating — stop the after-dinner snacks.

The most common fasting or time-restricted eating regimens are as follows:

• 16:8 . This means fasting for 16 hours and eating for 8 hours. For example, finish dinner at 7pm and have your first meal the next day at 11am. There are many other variations of this such as 14:10, 18:6, and 20:4.
• OMAD : This stands for “one meal a day.” As it sounds, this simply means eating only one meal for the entire day with no snacking. You can learn more about OMAD in our dedicated guide,  What you need to know about OMAD .
• Alternate-Day Fasting (ADF) : Finish dinner at 7pm Monday, don’t eat anything all day Tuesday, and have your first meal at breakfast or lunch on Wednesday. That’s an alternate-day fast. Read more about ADF here .
• 5:2 . Eat normally for five days during the weak and fast or eat very low calories (around 500 calories) two days of the week. The two days do not have to be consecutive days.

When starting out, we recommend starting small and building up. That may mean starting with a 14:10 pattern three days per week. As that becomes easier, you can try increasing the fasting window and/or increasing the number of fasting days per week.

Remember, fasting in this sense means no food; it does not mean no drinking. Staying well hydrated is an important part of succeeding with intermittent fasting. The best drinks are free from calories and sweeteners, meaning still or sparkling water, and tea or coffee without any additives.

What does intermittent fasting do?

The main benefits of intermittent fasting are  weight loss  and improving  metabolic health , including better blood sugar control in  type 2 diabetes .

There are different mechanisms to account for the success of intermittent fasting.

First, skipping meals and cutting out snacking naturally reduces the amount of calories one eats during the day. That’s why it is important to try  not  to eat more during your eating window to “make up” for the missed meal. That would negate one of the main benefits of fasting!

The second potential reason for IF’s success is its ability to lower insulin levels.  Studies show that fasting tends to lower insulin levels, although it is not scientifically clear the extent to which lower insulin levels can directly explain better weight loss.

However, a 2020 study from Dr. Ethan Weiss and colleagues created some doubt about whether short fasts of 16 hours, in the absence of any other dietary modification, can lead to improved weight loss and metabolic health.  The study’s authors concluded that time restricted eating was no better than eating throughout the day for weight loss.

We  wrote about this study , noting that the fasting group did not reduce caloric intake, which puts it at odds with other studies that have suggested at least part of the benefit of fasting comes from reduced caloric intake.

Clinicians familiar with intermittent fasting frequently report that people may respond differently to fasting — some may naturally restrict their calories, and others may feel increased hunger and increase their daily calories.  Knowing if intermittent fasting increases your hunger or cravings may be an important consideration to predict your success with fasting.

One other exciting benefit of intermittent fasting is its potential contribution to longevity. While human research of this nature is limited and very difficult to do, animal models suggest that intermittent fasting can trigger autophagy, which is a term for cellular recycling and disposal of older and potentially diseased cells; this could eventually lead to longer lifespans.  Does time restricted eating lead to living longer? We don’t have nearly enough data to draw any conclusions.

But even though human data on longevity are lacking, the other benefits of IF and its ease of use likely make it worth a try.

You can read more about the many impressive and inspiring  success stories  from people who have dramatically improved their health with intermittent fasting.

How to succeed with intermittent fasting

Since it saves time and money, many have no problem starting IF. Others, however, may find it challenging to start — especially when they are used to eating three meals and snacks every day. Here are some tips for success:

• Pick the right schedule to start.  You may have the urge to start with three- or five-day fasts, but we recommend focusing on success with time-restricted eating first, starting where you feel most comfortable (14:10, 16:8, etc). Then, if you are finding success, consider gradually increasing the fasting window. Fasts of longer than 36 hours should generally be done under the supervision of an experienced health care provider.
• Stay hydrated.  Fasting means not eating. It doesn’t mean not drinking. Not only will hydration help mitigate many side effects, but it also gives you something to do that mimics eating and puts something in your stomach. This can help both physically and psychologically to better ensure fasting success. How do you know of you are well hydrated? You should have to urinate at least four times per day and your urine should be clear, not yellow.
• Distract and occupy yourself during your usual meal and snack times.  If we are honest with ourselves, most snacking isn’t to avoid malnutrition. It is a habit or a distraction. One solution is to distract yourself with something else! Go for a walk, read a book, play a game, do a crossword puzzle, or otherwise. Just do something to get you out of your snacking routine that will keep you from reflexively thinking about it.
• Make sure your meals are full of nutrient-dense foods with adequate protein.  Studies show that keto diets and higher-protein diets help with satiety. That may be why many low-carb clinicians find people following these diets have greater success with fasting. Read more about what we mean by  adequate protein in our evidence-based guide .
• Understand that  hunger  comes and goes in waves and is a natural feeling.  It seems we have been trained to fear hunger and avoid it at all costs. But hunger is a natural feeling that we can learn to acknowledge and then ignore. You may find it goes away just as quickly as it came on.

By following these fasting tips, you will set yourself up for success and be much more likely to incorporate intermittent fasting as part of your daily routine.

You can also learn more about the potential  side effects of intermittent fasting  in our evidence-based guide.

Fasting precautions and who should not fast

Most people can safely and successfully incorporate fasting into their daily lives with few, if any, side effects. However, there are some specific individuals who should avoid fasting, or at least do so under the careful guidance of an experienced clinician.

• Pregnancy and breastfeeding  both significantly increase energy demands in the mother. Fasting may deprive her and her baby of essential calories and nutrients.
• Women trying to get pregnant  may find fasting disrupts their menstrual cycle and lowers their fertility. However, women with infertility from PCOS may find benefit with low-carb diets and possibly with time-restricted eating. This should be monitored with an experienced clinician.
• Kids  have higher energy demands due to their rapid growth rates. Fasting is generally not appropriate or safe.
• Anyone who is underweight or malnourished  should also avoid fasting.
• Anyone with a history of eating disorders such as anorexia or bulimia  should avoid fasting, as it could trigger eating disorder tendencies. Also, a history of anorexia or bulimia may alter the perception of being underweight or malnourished, potentially placing the individual at risk with fasting.
• Anyone taking medications that lower blood sugar  — such as insulin, sulfonylureas, and others — should only fast with the guidance of an experienced clinician. You can provide your clinician with  this handout  that gives guidance on how to best manage these medications with fasting. However, you should not attempt this on your own, as there is a significant risk of dangerous and potentially life-threatening low blood sugar levels.

Will I also lose muscle when I fast?

Most of the data regarding fasting and muscle loss come from studies looking at fasting for days to weeks.  In our  in our evidence based guide  we examine the most relevant scientific research about IF, concluding that it’s very unlikely to see significant muscle loss with IF, especially if eating adequate protein and engaging in resistance training.

Can I work out when I fast?

Yes! You definitely can. In fact, exercising while fasting is a good way to deplete glycogen stores and tap into fat stores for energy. However, it is not clear if fasted exercise leads to greater weight or fat mass loss.

While high-intensity exercise or prolonged exercise in non-fat adapted individuals may be challenging, most people find no trouble at all with moderate-intensity exercise and resistance training when fasting.

Isn’t breakfast the most important meal of the day?

No! While that is a message we have heard for decades, there is no science to support the claim. In fact, scientific studies show the opposite — there is no need to eat breakfast. Skipping your morning meal gives your body more time to burn fat for energy. Since hunger is lowest in the morning, it may be easiest to skip breakfast and break your fast later in the day.

Can kids or the elderly fast?

As we mentioned in our precautions section, kids should not fast given their energy demands for growth. Elderly people, on the other hand, have no specific contraindication to fasting as long as they don’t have an underlying illness that may preclude them from doing so.

In summary, intermittent fasting or time restricted eating could be the easiest way to improve your metabolic health and lose weight. It saves time, saves money, and you can succeed no matter what your preferred dietary pattern.

The key is doing it in a way that feels sustainable and fits into your lifestyle. Give it a try!

What is healthy weight loss?

Guide Weight loss isn’t all the same. Read our guide to find out how to make sure you’re losing weight in a healthy way.

Intermittent fasting for healthy weight loss

Guide Intermittent fasting can help with health and weight loss. Here are our top tips to make sure you lose weight in a healthy way.

Time-restricted eating — a detailed IF guide

Guide Keep your eye on the clock, only eating during a planned window each day. It’s that easy, and it can help with weight loss.

These results are not consistent across all studies, as we detail later in this guide.

Cell Metabolism 2020: Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in patients with metabolic syndrome [nonrandomized study, weak evidence]

This is based on clinical experience of low-carb practitioners and was unanimously agreed upon by our low-carb expert panel. You can learn more about our panel  here   [weak evidence] .

Currently, the literature lacks intermittent fasting or time restricted eating studies comparing different baseline diets, so for now we must rely upon clinical experience.

Nutrition Journal 2010:  The impact of religious fasting on human health   [overview article; ungraded]

High quality data to prove this claim are hard to find, but the following references suggest that it may be the case.

European Journal of Clinical Nutrition 2002:  The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic [review article, ungraded]

BMC Public Health 2003: Effects of Greek Orthodox Christian Church fasting on serum lipids and obesity   [observational study; weak evidence]

Procedures of the Natural Academy of Science U.S.A 2014:  Meal frequency and timing in health and disease [overview article; ungraded]

These are the definitions we use at Diet Doctor. As of yet, there are no universally accepted definitions of time-restricted eating and short- or long-term fasts.

Many of the studies regarding intermittent fasting and weight loss investigated restricting calories to very low levels for a limited time, like one or more days per week (eg, 500 calories per day). Actual fasting means restricting calories to nearly zero for a time, so it may or may not be more effective.

JBI Database of Systematic Reviews and Implementation Reports 2018:  Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis   [strong evidence]

Obesity Reviews 2017:  Short‐term intermittent energy restriction interventions for weight management: a systematic review and meta‐analysis   [strong evidence]

Obesity (Silver Spring) 2016:  A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity   [moderate evidence]

The American Journal of Clinical Nutrition 2015:  Health effects of intermittent fasting: hormesis or harm? A systematic review   [systematic review of RCTs and observational studies; moderate evidence]

Intermittent fasting and type 2 diabetes:

JAMA Network Open 2018:  Effect of intermittent compared with continuous energy restricted diet on glycemic control in patients with type 2 diabetes: a randomized noninferiority trial   [moderate evidence]

Diabetes Research and Clinical Practice 2016:  The effects of intermittent compared to continuous energy restriction on glycaemic control in type 2 diabetes; a pragmatic pilot trial   [moderate evidence]

BMJ Case Reports 2018:  Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin   [case reports, very weak evidence]

In addition to being responsible for controlling blood sugar levels, higher insulin levels also promote the storage of fat.

The following studies show reduced insulin levels with intermittent fasting, some of which also demonstrate improved fat mass loss. While this does not prove cause and effect, it makes the mechanistic hypothesis plausible. Further studies are required for definitive proof of cause and effect.

International Journal of Obesity 2011:  The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women   [moderate evidence]

The following study was a systematic review of 4 RCTs selected using the GRADE system to pick the highest-quality evidence available.

Cureus 2018:  Intermittent fasting: the choice for a healthier lifestyle   [systematic review of randomized trials; strong evidence]

The following study showed similar timing of insulin secretion with short term fasting but at a much lower amplitude, therefore making the overall insulin levels persistently higher for the regularly eating cohort.

Diabetes 2002:  Effects of fasting on physiologically pulsatile insulin release in healthy humans [nonrandomized study, weak evidence]

The following study showed fasting improved HOMA-IR, which is a measurement of insulin sensitivity.

Journal of Clinical Medicine 2019:  The Effectiveness of Intermittent Fasting to Reduce Body Mass Index and Glucose Metabolism: A Systematic Review and Meta-Analysis   [systematic review of randomized trials; strong evidence]

JAMA Internal Medicine 2020:  Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity   [randomized trial; moderate evidence]

As we mentioned earlier, this nonrandomized study reported significant metabolic health benefits with 14 hours of fasting even in the absence of any advice about what or how much to eat. One explanation is that the subjects ate better than their usual diet simply because they were being monitored as part of a study — sometimes called “the Hawthorne effect.”

This is based on the consistent clinical experience of practitioners familiar with intermittent fasting.  [weak evidence]

Aging Research Reviews 2016:  Impact of intermittent fasting on health and disease processes   [overview article]

Cell Metabolism 2014:  Fasting: molecular mechanisms and clinical applications   [overview article]

NEJM 2019:  Effects of Intermittent Fasting on Health, Aging, and Disease [overview article; ungraded]

Other potential mechanisms include the impact on mTOR

Nutrients 2020:  Mechanisms of Lifespan Regulation by Calorie Restriction and Intermittent Fasting in Model Organisms [overview article; ungraded]

Obesity Reviews 2015:  Do ketogenic diets really suppress appetite? A systematic review and meta-analysis   [strong evidence]

European Journal of Clinical Nutrition 2013:  Ketosis and appetite-mediating nutrients and hormones after weight loss [non-controlled study; weak evidence]

In fact, several studies have shown that when people dramatically cut back on carbs but are allowed as much protein and fat as they want, they end up automatically eating less because they’re no longer as hungry.

Annals of Internal Medicine 2014:  Effects of low-carbohydrate and low-fat diets; a randomized trial   [moderate evidence]

Annals of Internal Medicine 2005:  Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes   [non-randomized trial; weak evidence]

Nutrition & Metabolism 2005:  A low-carbohydrate, ketogenic diet to treat type 2 diabetes   [non-controlled trial; weak evidence]

International Journal of General medicine 2013:  Hunger can be taught: Hunger recognition regulates eating and improves energy balance [overview article; ungraded]

This is based on the consistent clinical experience of practitioners familiar with intermittent fasting. [weak evidence]

In shorter studies, most data suggest that muscle loss is not an issue. In a 2016 randomized, controlled trial, obese adults were assigned to either fast every other day or eat a calorie-restricted diet every day for eight weeks. Those in the intermittent fasting group showed less slowing in metabolic rate and greater improvement in body composition after 32 weeks of follow up compared to people in the calorie-restricted group:

Other studies of intermittent fasting have shown beneficial effects on metabolic rate and/or body composition:

American Journal of Clinical Nutrition 2007:  A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults   [moderate evidence]

American Journal of Clinical Nutrition 2000:  Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine   [weak evidence]

The American Journal of Clinical Nutrition 2005:  Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism   [weak evidence]

Journal of International Science and Sports Nutrition 2014:  Body composition changes associated with fasted versus non-fasted aerobic exercise [randomized trial; moderate evidence]

Scandinavian Journal of Medicine & Science in Sports 2018:  Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis   [meta-analysis of randomized and non-randomized studies; moderate evidence]

The term “fat adapted” refers to the ability to efficiently produce energy from fat instead of glucose.

The old idea that breakfast is important for health or weight control is mainly based on observational studies, a notoriously weak form of evidence.

When tested, this idea does not appear to hold up, at least not for weight loss. A recent meta-analysis of randomized clinical trials found that people assigned to skip breakfast ate less overall and lost more weight than those assigned to eat breakfast daily:

British Medical Journal 2019:  Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials   [strong evidence]

Even the observational data is inconsistent, for example, with this finding from the study below: “Compared to breakfast eating, skipping breakfast was significantly associated with better health-related quality of life and lower perceived stress.”

International Journal of Environmental Research and Public Health 2018:  Eat or skip breakfast? The important role of breakfast quality for health-related quality of life, stress and depression in Spanish adolescents   [observational study; weak evidence]

Obesity (Silver Spring) 2013:  The internal circadian clock increases hunger and appetite in the evening independent of food intake and other behaviors [non-randomized study; weak evidence]

Your complete guide to intermittent fasting - the evidence

This guide is written by Dr. Bret Scher, MD and was last updated on November 16, 2022. It was medically reviewed by Dr. Michael Tamber, MD .

The guide contains scientific references. You can find these in the notes throughout the text, and click the links to read the peer-reviewed scientific papers. When appropriate we include a grading of the strength of the evidence, with a link to our policy on this. Our evidence-based guides are updated at least once per year to reflect and reference the latest science on the topic.

All our evidence-based health guides are written or reviewed by medical doctors who are experts on the topic. To stay unbiased we show no ads, sell no physical products, and take no money from the industry. We're fully funded by the people, via an optional membership. Most information at Diet Doctor is free forever.

Read more about our policies and work with evidence-based guides , nutritional controversies , our editorial team , and our medical review board .

Should you find any inaccuracy in this guide, please email [email protected] .

Intermittent Fasting: A Beginner's Guide

What is intermittent fasting.

• Budget friendly. Foods for this diet are easy to find at a typical grocery and don’t require expensive or specialty food items.
• Vegan or vegetarian friendly. Recipes can be easily modified for a vegan or vegetarian diet.
• Gluten-free friendly. Recipes can be easily modified and still follow a gluten-free diet.
• Halal friendly. Recipes can be easily modified and still follow the diet.
• Kosher friendly. Recipes can be easily modified and still follow the diet.
• Low-carb. Low-carb diets contain significantly less calories from carbs than the government’s 45% to 65% recommendation.

How does Intermittent Fasting work?

• With intermittent fasting hours, you may also consume fewer calories overall throughout the week. 
• Some experts suggest following a low-carb eating plan on normal feeding days.
• Intermittent fasting may pull in physiologic aspects of other diets like keto (fat burning) and glycemic index (low-GI foods to control blood glucose levels). 

The types of intermittent fasting include:

• Time-restricted eating. One of the more popular approaches to intermittent fasting is called time-restricted eating. This approach calls for eating only during an eight-hour window and fasting for the remaining 16 hours of the day. The fasting period is the "rest" period to allow the body to metabolize the calories that were consumed during the feeding phase.
• 5:2 plan. In this plan, you follow a normal, healthy meal pattern for five days a week. During the other two nonconsecutive days, you consume only one meal that consists of 500 to 700 calories each day, which is a caloric deficit for most healthy individuals,
• Alternate-day fasting. Every other day, on your fasting day, you consume anywhere from zero calories to only about 500 daily calories, depending on how strict an approach you choose.
• Modified alternate-day fasting. On fasting days, you’ll limit your food consumption to 20% to 25% of your regular consumption. On alternate days, you eat normally. 
• Eat, stop, eat. This approach to intermittent fasting entails selecting one or two nonconsecutive days each week to fast for 24 hours. During the other non-fast days, you can eat as you normally would to meet your caloric and nutritional needs.
• Fasting-mimicking diet . You severely restrict your calorie intake every three to four months for five consecutive days. 

Can I Lose Weight on Intermittent Fasting?

• Alternate-day fasting has been shown to be an effective dietary method equivalent to very low-calorie dieting for some patients ( 1 ).
• In another study, obese participants who alternated days of fasting with either high-fat or low-fat diets lost weight and inches from their waist ( 2 ).
• However, one study showed that time-restricted diets were no more effective in helping people lose weight than consuming food throughout the day ( 3 ).

Short-Term Weight Loss

• Different types of intermittent fasting have shown positive results on weight loss ( 4 ).
• Intermittent fasting plans helped participants lose an average of 7 to 11 pounds after 10 weeks, according to one study ( 5 ). There were also no significant differences in weight loss amounts or body composition changes between the intermittent fasting and continuous calorie restriction groups. Although participants in the intermittent fasting groups lost weight and demonstrated a decrease in leptin - a hormone that suppresses appetite - there was no significant increase in appetite.

Long-Term Weight Loss

• In a systematic review, researchers found that intermittent fasting led to weight loss similar to standard calorie cutting – about 15 pounds on average. Specifically, among individuals practicing alternate-day fasting regimens, self-reported hunger on fasting days can be significant and does not decrease over time, making this a questionably effective plan for long-term weight loss ( 1 ).

Weight Maintenance and Management

• One study showed that obese men who dieted for two weeks and then took two weeks off for 30 weeks lost more weight than those who dieted continuously with no downtime. The men kept the weight off for six months ( 6 ).
• A study of 100 adults with obesity over one year found that alternate-day fasting was similar – but not superior – to daily calorie restriction for losing weight or maintaining weight loss ( 7 ).

Skinless chicken

Doing Intermittent Fasting on a Budget

• Meat is often the most expensive item in your cart. Challenge yourself to go meatless a few days a week. 
• Pay attention to the cost per ounce rather than the total cost when choosing between two food products. Most stores provide this information on the shelf tags. 
• Plan your meals and snacks ahead of time to avoid both impulse buys and food waste. 
• Rely on canned and frozen vegetables and fruits, which cost less fresh. 
• When you purchase fresh fruits and vegetables, choose those in season. 
• Don’t give into “buy one, get one” offers or bulk food store savings if you’ll never eat it all before it spoils. 
• Don’t shy away from the store brand.

Is Intermittent Fasting Easy to Follow?

• By eating nutritious foods on both fasting and feeding days, you probably don’t need a supplement. If you choose to take vitamin or mineral supplements, experts suggest doing so on non-fasting days. Some supplements contain ingredients that may not be compatible with fasting guidelines, while other supplements are better absorbed when taken with food.
• You don’t have to change the foods you normally eat. But you may find daily or twice-weekly fasting periods challenging and need to plan your social life and activities around them.
• Intermittent fasting can be pretty convenient. The minimalist nature of fasting makes it reasonably convenient. The most significant inconvenience is the very premise of intermittent fasting – ignoring hunger and consuming few calories during your chosen fasting periods.
•   Alcohol is fair game most days of the week with 5:2 intermittent fasting. On fast days, however, your calories are so precious that it’s better to spend them on foods with nutritional value. That way, you’ll also avoid drinking on an emptier stomach.
• You’ll probably be hungry. Nutrition experts emphasize the importance of satiety, the satisfied feeling that you’ve had enough to eat. However, there’s a good chance, at least toward the beginning, you won’t feel particularly full on fast days or fasting periods.
• Intermittent fasting is only an eating pattern, but that doesn’t mean you should stop exercising. Being physically active lowers your risk of heart disease and diabetes, helps keep weight off and increases your energy level. The Centers for Disease Control and Prevention recommend getting about 30 minutes of moderate-intensity exercise – like brisk walking – most or all days of the week.

Who Should Not Try the Intermittent Fasting?

• Women who are trying to get pregnant or are already pregnant.
• Anyone with Type 1 diabetes is affected by meal timing and requires consistent eating patterns . Individuals with a history of hypoglycemia should avoid intermittent fasting. 
• Children – who are still growing and developing – should not do intermittent fasting.
• People with eating disorders should not attempt fasting, nor should those who are underweight.
• Anyone with other medical conditions, particularly gout or liver, kidney or heart disease, should talk to their doctors in advance, as should anyone taking prescription medications. 
• Athletes or those with an intense exercise regimen. 
• If you are on medication that requires food for absorption, this plan won’t work for you if the timing doesn’t work out. 

No counting carbs, points or calories.

No off-limit foods or food groups.

Has proven health benefits.

Lacks in-depth nutritional guidance.

Tedious portioning, meal planning or prep.

Eating out is limited.

You’ll likely get hungry.

Unsafe for some people.

Lots of rules to remember.

Could fall short nutritionally.

How to Get Started on the Intermittent Fasting

• Decide which fasting format to try. 
• Fill your kitchen with nutrient-dense, whole foods . 
• Consider easing your way into it by skipping breakfast or postponing breakfast. 
• Drink plenty of water to stay hydrated . 
• Avoid strenuous exercise on fasting days.

Success Stories for the Intermittent Fasting and Tips from Real People

Jackie Moravek, a 35-year-old from Kalamazoo, Michigan, “absolutely loves” intermittent fasting. She was first introduced to intermittent fasting through her church as a short-term, spiritual fast. She started intermittent fasting in June of 2020 and continues to follow the routine, now hosting a blog and YouTube channel to teach others about intermittent fasting.

At the beginning of her journey, Moravek read the book “Fast. Feast. Repeat.” by Gin Stephens, listened to podcasts and spent time in Facebook groups to learn more about other peoples’ success stories.

Moravek found that she started to lose weight steadily – 1 to 2 pounds per week – until she eventually lost a total of 35 pounds. She noticed that she felt much better physically.

"Because I wasn't counting calories or restricting foods, I had such a mental burden lifted. I was able to not obsess over what I wanted to eat, what I did eat, what I shouldn't have eaten and what I ate too much of," Moravek says.

Long term, she’s also found that her eyesight improved, her fatty liver showed signs of reversal on blood tests and she's maintained weight loss. Moravek recommends joining a community like a Facebook group or watching YouTube channels for those looking to try the diet. She says,

“It’s encouraging to learn from others,” she says. “You can learn to fast without immediately going to 22 hours fasted a day. You can increase to whatever works best for you.”

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Support and Resources for the Intermittent Fasting

It’s easy to find recipes and resources for intermittent fasting. Some of the most popular books include:

• “Complete Guide To Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting” by Dr. Jason Fung and Jimmy Moore
• “Fast. Feast. Repeat: The Comprehensive Guide to Delay, Don't Deny® Intermittent Fasting – Including the 28-Day FAST Start” by Gin Stephens
• “The Fast 800: How to Combine Rapid Weight Loss and Intermittent Fasting for Long-Term Health” by Dr. Michael Mosley 
• “The FastDiet - Revised & Updated: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting” by Dr. Michael Mosley

There are also many apps to help you plan your new lifestyle, including

• Window. One of the best apps for newbies, this app alerts you when you're in your eating and fasting windows. Also, you can sync the information with your Apple Health app or Apple Watch. 
• Fastic. This app includes a fasting timer, step and activity counters, recipes and community support.
• Fastient. Great for tracking your intake and overall progress, this app also allows you to journal as you go.
• BodyFast. If it’s coaching that you’re looking for, this is the right app. Although it’s not a substitute for a dietitian or doctor, BodyFast will provide motivation, recipes and tips to help keep you on track. 

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Why Trust U.S. News

With the help of our Best Diets panel of nationally-recognized experts in nutrition, obesity, food psychology, disease management, we developed a survey in partnership with The Harris Poll. The survey asked the panel to carefully compare diets for their nutritional completeness, health risks and benefits, long-term sustainability and evidence-based effectiveness. You can see our full methodology here .

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This article is based on reporting that features expert sources.

The U.S. News Health team delivers accurate information about health, nutrition and fitness, as well as in-depth medical condition guides. All of our stories rely on multiple, independent sources and experts in the field, such as medical doctors and licensed nutritionists. To learn more about how we keep our content accurate and trustworthy, read our  editorial guidelines .

Amidor is an award-winning nutrition expert and Wall Street Journal bestselling author of multiple books, including "The Best 3-Ingredient Cookbook," "Diabetes Create Your Plate Meal Prep Cookbook" and "The Family Immunity Cookbook." She is based in New York.

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Table of Contents

What is intermittent fasting (if), the science behind intermittent fasting and weight loss, the benefits of intermittent fasting for weight loss, how to use intermittent fasting for weight loss effectively, ensuring long-term stability of intermittent fasting, potential risks and precautions you should know about, where can you learn more about intermittent fasting and weight loss.

• Weight Management

Everything You Should Know About Intermittent Fasting for Weight Loss

Fasting has been practiced for thousands of years and in many different contexts. One popular method known for promoting weight loss is intermittent fasting (IF).

IF involves restricting yourself to only eating during specific times of the day, which may reduce your caloric intake and help you shed excess pounds.

However, before implementing intermittent fasting, you’ll need to research which variation would work best for you to ensure long-term sustainability.

In this article, we’ll take a closer look at everything you need to know about intermittent fasting – including how to do it safely and effectively.

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Intermittent fasting — which is also known as time-restricted eating (TRE) — is a dietary approach where an individual alternates between periods of eating. It involves cycling between designated eating and fasting times.

When you’re intermittent fasting, you won’t need to focus on what you eat, but rather be mindful of when you eat.

This approach has gained popularity due to its potential health benefits , including weight loss and improved cognitive function.

There are a few different ways you can implement an intermittent fasting pattern into your routine. Common methods include:

The 16:8 method: Involves fasting for 16 hours and eating during an 8-hour window

The 5:2 method: Involves eating regularly for five days of the week and significantly reducing your caloric intake for two nonconsecutive days

The 20:4 or Warrior Diet: Involves 20 hours of fasting and a 4-hour eating window

OMAD (One Meal a Day): Involves fasting for 23 hours and eat all your daily calories in one meal

Alternate-Day Fasting: Involves switching between days when you consume very few calories and regular eating days

Remember, intermittent fasting may work well for some people, but it might not be suitable for everyone. Always consult with your doctor first.

Research suggests that, compared to a calorie restriction group, intermittent fasting may have a more significant impact on the body’s metabolism and hormone regulation.

These are two components that play a central role in weight management.

One of the key mechanisms of intermittent fasting is that it can alter the hormones that control hunger and fat storage.

During fasting periods, insulin levels drop and allow the body to access stored fat for energy. This shift in metabolism promotes fat-burning and contributes to weight loss over time.

Intermittent fasting may also enhance the body’s insulin sensitivity – another crucial part of regulating blood sugar levels.

Stable blood sugar levels make it easier for the body to burn fat and control hunger, both of which help with weight loss.

When we consume meals and snacks throughout the day, our blood sugar rises, which makes it more difficult for the body to burn fat. The body may also become used to these elevated insulin levels.

Over time, this can lead to insulin resistance, which may increase the amount of fat the body stores.

With intermittent fasting, the body may experience extended periods of lower insulin production, which may improve overall sensitivity.

Lastly, intermittent fasting stimulates the release of the human growth hormone (HGH). This hormone plays a role in preserving lean muscle mass and promoting fat breakdown.

The increased levels of HGH during fasting periods contribute to weight loss and positive changes in your body.

Caloric reduction without continuous calorie restriction

Being in a calorie deficit — or a state where you burn more calories than you consume — is a proven way to promote weight loss.

Intermittent fasting simplifies the process of being in this deficit since it naturally reduces the number of calories you consume by restricting how often you eat.

This can help you naturally eat smaller and fewer portions while paying more attention to the food you consume.

It also means you don't have to engage in obsessive calorie counting or eliminate your favorite foods from your diet, which makes intermittent fasting an easier way to lose weight.

Enhanced metabolic rate and fat-burning

Fasting periods may trigger a shift in the way the body stores energy. With reduced insulin levels, the body starts tapping into its stored fat reserves for fuel.

This helps to promote a thermic effect, which is a process that increases fat-burning and weight loss over time.

Some studies suggest that this thermic effect may also temporarily increase the body’s metabolic rate.

This may enhance weight loss efforts because the body uses more energy to digest food.

Appetite regulation

Intermittent fasting may help regulate the hormones that control appetite — ghrelin and leptin — which reduces feelings of hunger.

This means that you may feel fuller for longer, and you’ll need less food to satisfy your appetite.

Some people may even find that they naturally consume fewer calories because they know their hunger cues much better.

Control compulsive eating

Structured eating windows can help you maintain better control over compulsive snacking, which reduces the likelihood of binge eating.

By creating these designated times for eating, people may develop healthier eating habits and manage their calorie intake better.

Choose the correct method

The first step to a successful intermittent fasting journey is to choose the right method for your lifestyle and preferences.

For example, if you decide to use the 16:8 method, you’ll have a 16-hour fasting period when you can’t eat.

After that, you’ll have an 8-hour window for consuming meals so make sure you’ll have time to cook and eat during this period.

Choosing a plan that aligns with your daily routine and dietary habits will make it easier to stick to it in the long term.

Eat nutrient-dense foods

When it’s time to eat, opt for nutrient-rich foods that can help the body sustain itself. This means eating meals rich in vitamins, minerals, and other nutrients.

Include lean proteins, whole grains, fruits, vegetables, and healthy fats in your meals. Not only do these foods promote weight loss, but they also contribute to your overall health.

Stay hydrated

Consuming enough fluids — especially during fasting periods — is essential. You can either drink water or opt for herbal teas and black coffee.

These drinks may curb hunger and help your body to function properly during fasting periods. Adequate hydration can also support your metabolism and help you feel more alert.

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Listen to your body

Pay attention to your body’s signals and adjust your fasting pattern accordingly.

If you’re feeling excessively hungry or fatigued, consider reducing your fasting period.

For example, if you are following a 20:4 method and feel like you’re struggling to fast for such a long period of time, you can switch to the 16:8 method.

This means you’ll have more time to eat with fewer hours in between meals.

It’s important to remember that intermittent fasting shouldn’t lead to discomfort, so it’s crucial to strike a balance that works for your lifestyle.

Plan meals in advance

Planning your meals and snacks in advance can help you make healthier choices during your eating periods.

Having a meal plan also reduces your risk of overeating and consuming excess calories.

Intermittent fasting is a flexible way of eating that can be tailored to fit into various lifestyles – making it a great option for people looking for a long-term solution to weight loss.

The key to achieving success with intermittent fasting is to view it as more than just a weight loss strategy. Instead, it can be a powerful tool to support your overall health.

By focusing on the broader health benefits, you may be able to shift your perspective and feel more motivated to continue with intermittent fasting, too.

Thinking of intermittent fasting as a lifestyle change will also empower you to make mindful eating decisions that help to improve your relationship with food.

With your structured eating schedule, you’ll need to plan nutritious meals and snacks in advance.

This helps you to become more aware of what you are eating, which may encourage you to make healthier food choices.

Over time, this can help you create better eating habits and maintain a healthy body weight.

As with any dietary approach, intermittent fasting comes with its set of potential challenges and considerations that should be taken into account for a safe and effective experience.

Let’s take a closer look at what these are.

Initial adjustment period

For many individuals, adjusting to fasting periods can be challenging. You may experience hunger, irritability, and low energy during the first few days or weeks.

It's important to be patient with yourself during this transition period as your body adapts to the new eating schedule.

Overeating during eating windows

While intermittent fasting can promote better appetite regulation, some people may be tempted to overcompensate for fasting periods by consuming excess calories during eating windows.

This type of disordered eating can cause weight gain, which may put you at risk of developing metabolic conditions like obesity.

To avoid excessive food intake, focus on following a healthy diet filled with balanced, nutrient-dense meals and practice portion control.

Consult a healthcare professional

Before making any significant dietary changes, it's crucial to consult with a healthcare professional.

This is also essential for individuals with preexisting health conditions like diabetes, heart disease, or metabolic and eating disorders.

Your doctor can provide personalized guidance and help you determine whether intermittent fasting is safe and appropriate for your health needs. Medications and fasting

If you are taking medications, consult with your healthcare provider to ensure that fasting does not interfere with their effectiveness or safety.

Some medications may need to be adjusted to accommodate fasting periods.

Pregnancy and breastfeeding

Intermittent fasting is generally not recommended for pregnant or breastfeeding women , as this diet regimen may not provide sufficient nutrients for both the mother and the baby.

It's essential to prioritize adequate nutrition during these life stages or consult with your doctor if you are concerned about your weight at this point. Individual responses

Keep in mind that everyone's body responds differently to intermittent fasting. What works for one person may not work for another.

Be open to adjusting your fasting pattern or duration to suit your unique requirements and preferences.

Long-term sustainability

While intermittent fasting can be a long-term lifestyle choice, it may not suit everyone in the long run.

If you find that it becomes unsustainable or negatively affects your health or well-being, reassess your approach and consider alternative weight and fat loss strategies.

If you’re concerned about weight management or want to know more about strategies like intermittent fasting, LifeMD is here to help.

Our team of doctors can assist you with information and provide guidance on how to effectively maintain a healthy weight — all from the comfort of your home. LifeMD also offers a Weight Management Program , designed to help you get started on a personalized weight loss journey.

Make an appointment today to learn more about intermittent fasting and how LifeMD can help you manage your weight.

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Your Guide to Intermittent Fasting for Weight Loss

Tired of fad diets? Intermittent fasting can help you lose weight without giving up your favorite foods. Here’s everything you need to know, according to experts.

The popularity of intermittent fasting has grown in recent years, but this trendy dietary lifestyle is hardly new. History shows that this age-old eating practice has been embraced by everyone from ancient Greek civilizations to monks. Below, we take a deep dive into intermittent fasting, including different ways to make it work for you.

What Is Intermittent Fasting?

“Intermittent fasting is a term used to describe various eating patterns that cycle between scheduled periods of eating and not eating,” says Mopelola Adeyemo, MD, MPH , a clinical instructor in the division of clinical nutrition at UCLA Health in Los Angeles. “It’s a form of caloric restriction, so during the fasting periods you eat either very little or nothing at all.”

Previous generations adopted this eating pattern to improve their spiritual, mental, and physical health. But today, the main focus is on weight loss.

Does Intermittent Fasting Work for Weight Loss?

Any time you’re in a calorie deficit, you’re more likely to lose weight. By restricting when you eat, you often eat less simply by skipping meals. However, a recent study conducted at the University of Illinois Chicago concluded that when 90 adults categorized with obese BMIs were divided into three groups — one control group, one group that reduced calories by 25 percent, and one group that only ate during an eight-hour window — there was virtually no difference between the group that reduced calories and the one that followed an intermittent fasting pattern. 

How Does Intermittent Fasting Impact Hunger?

If you’re worried that restricted eating windows may make you even hungrier, rest assured this isn’t typically the case, at least not for the long term. “When you’re first starting, it’s common to experience increased hunger or cravings as your body adjusts,” says New York City–based Amy Shapiro, RD, founder of Real Nutrition NYC . “The adjustment period typically lasts for a few days and may affect hormone levels involved in hunger and satiety. Some research suggests that fasting may potentially reduce hunger and increase feelings of fullness over time.”

How Much Weight Can You Lose on Intermittent Fasting?

The amount of weight you will lose while intermittent fasting largely depends on several factors, including your average calorie intake, age, sex, activity level, and, of course, your genetics . 

“A recent review of 27 clinical trials on intermittent fasting found that individuals lost between 0.8 and 13 percent of their body weight with intermittent fasting,” says Dr. Adeyemo. “Study durations ranged from two weeks to 26 weeks. Still, it is important to remember that every individual is unique, so responses will vary. To achieve the best results, pair intermittent fasting with adequate exercise and healthy food choices.”

How Does Intermittent Fasting Compare to Other Strategies for Weight Loss?

The truth is that intermittent fasting may work wonders for your weight loss goals or not do anything at all. “The best diet for weight loss is one that aligns with the individual and their preferences and health goals,” says Shapiro. “You should also make sure that you’re promoting sustainable eating habits and getting a balanced intake of nutrients. It’s most important to choose a dietary approach that you can maintain long term.”

Types of Intermittent Fasting

There are several different variations of intermittent fasting, so it’s important to find the method that works best for you. Adeyemo breaks down the basics below.

Time-Restricted Eating 

This is the most popular method, according to Adeyemo. “It involves eating during an 8-hour window, then fasting for 16 hours,” she says. “Another method is 12:12, which involves a 12-hour fasting period followed by a 12-hour eating window.”

Alternate-Day Fasting

Alternate-day fasting, says Adeyemo, requires you to fast for 24 hours followed by an eating period. “For example, you don’t eat from lunch one day until lunch the next day,” she explains. “This can be done a few times per week on nonconsecutive days and involves eating normally on your non-fasting days.”

Modified Fasting

“Also known as the 5:2 method, modified fasting involves eating 20 to 25 percent of your estimated caloric needs on fasting days, then 125 percent of your caloric needs on non-fasting days,” says Adeyemo.

Pros and Cons of Intermittent Fasting, According to a Lose It! Dietitian

The simplicity of intermittent fasting may sound appealing, especially if you’ve struggled with fad diets in the past, but the truth is that there are still plenty of factors to consider before you adopt this dietary lifestyle. We recently chatted with Anna Smith, a registered dietitian for Lose It!, about the pros and cons of intermittent fasting. Here’s what she had to say.

Pros of Intermittent Fasting

It’s flexible. “There’s not as much emphasis on what to eat. This freedom feels nice if you’re used to diets that restrict food groups or if you need a break from counting calories.”

It’s simple. “If you’re a habitual breakfast skipper, waiting to eat until later is usually not a huge adjustment.”

It forms good habits. “It sets a firm boundary in the evening to help you break any mindless nighttime munching.”

It’s good for your health. “It can be a good plan for weight loss, but many also see improvements in their lipids and blood pressure, according to research .”

Cons of Intermittent Fasting

It can be tough if you have an erratic schedule. “It can be a really difficult diet to adhere to for those who work 12-hour shifts like nurses or find themselves up late like Uber drivers and students. You may need a snack to fuel your energy levels.”

It may stifle your social life. “Social gatherings can be tricky if they are outside your eating window.”

You might not lose weight. “While the emphasis is technically on when to eat, it is possible to go over your calorie goal in your eating window. If you suddenly have to restrict when you eat and what you eat, it can feel overly restrictive.”

There can be side effects. “ Research shows that headaches, mood swings, and constipation are some of the most common side effects.”

Is Intermittent Fasting Right for Everyone?

Like any big lifestyle change, intermittent fasting isn’t right for everyone. Certain members of the population — including people who are pregnant or breastfeeding, individuals with diabetes, anyone who’s had an eating disorder, children, and adolescents, according to Johns Hopkins Medicine — should assess their health status before adopting this eating plan because the risks can outweigh the benefits in some cases. 

“Fasting periods can serve as a trigger for disordered eating,” says Adeyemo. “For people with diabetes, alternating between fasting and feeding periods may require adjustments in medications to prevent varying blood sugars. And if you’re pregnant or breastfeeding, the body requires more calories to maintain breast milk supply or provide adequate nourishment to a growing fetus. So it’s important to talk to your healthcare provider before starting any new diet.”

Tips to Get Started on Intermittent Fasting

If you’ve decided intermittent fasting is the perfect way to meet your weight loss goals, you’re definitely in good company. A 2022 survey of 901 Americans ages 19 to 81 concluded that 80 percent of them had dieted at some point in their lives, and 44 percent of them were currently on a diet. The most popular way to lose? You guessed it! Intermittent fasting. 

Not sure how to get started? Rest assured it’s easier than it sounds, so don’t be intimidated. Shapiro shares her top five tips for beginners here.

• Start slowly, and gradually increase your fasting window over time.
• Stay hydrated to reduce feelings of hunger. Consider consuming herbal tea, black coffee, and sparkling water during your fasting periods to curb your appetite.
• Focus on nutrient-dense foods during periods of eating and avoid highly processed or sugary foods.
• Listen to your body and remain aware of how it feels during periods of fasting and eating.
• Be patient and remind yourself of the initial adjustment period and the importance of consistency if you want to experience any potential health benefits.

The Bottom Line

Intermittent fasting has been around for thousands of years, but it’s recently had a huge surge in popularity among celebrities and many others looking to drop unwanted pounds. Although the plan is incredibly flexible with several different eating methods, it isn’t a one-size-fits-all solution for weight loss woes. Always consult your doctor first and carefully weigh the risks and benefits before changing your current eating plan.

“The most important thing to consider when choosing a diet is to choose one that best aligns with your lifestyle and is sustainable,” says Adeyemo. “Intermittent fasting is not superior to other diets, but it has been shown to have numerous benefits. However, any significant changes in your diet should always be discussed with your healthcare provider to ensure that the changes match with your health needs and goals.”

Editorial Sources and Fact-Checking

• Ravussin E et al. Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation but Does Not Affect Energy Expenditure in Humans. Obesity (Silver Spring) . August 2019.
• Lin S et al. Time Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population. Annals of Internal Medicine . June 27, 2023.
• Welton S et al. Intermittent Fasting and Weight Loss: Systematic Review. Canadian Family Physician . February 2020.
• Naous E et al. Intermittent Fasting and Its Effects on Weight, Glycemia, Lipids and Blood Pressure: A Narrative Review. Nutrients . August 2023. 
• Shalabi H et al. Intermittent Fasting: Benefits, Side Effects, Quality of Life, and Knowledge of the Saudi Population. Cureus . February 2023.
• Intermittent Fasting: What Is It, and How Does It Work? Johns Hopkins Medicine . 
• 2022 & 2023 Intermittent Fasting Statistics and Trends. VitalityPro . 2022.

Dana Meltzer Zepeda

Dana is a Southern California-based freelance writer who specializes in health and fitness stories.

Sean Hashmi , MD, MS, FASN

Sean Hashmi, MD, MS, FASN, is a dedicated and experienced nephrologist and obesity medicine specialist based in Southern California.

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How one woman used intermittent fasting to lose 65 pounds in six months

At 337 lbs, health and beauty influencer Janielle Wright was afraid she would die. Her body was in pain and she had trouble breathing at night.

“I was going to sleep worried that I wouldn’t wake up the next morning ,” Wright told NBC News BETTER.

She was also afraid that she wouldn’t live to see her 3-year-old daughter, Novah, grow up. That was when Wright, 28, realized something had to change.

“This is no way to live thinking you’re going to die because you’re overweight and you’re unhealthy,” she says.

Intermittent fasting is a time-restricted eating method where you only allow yourself to eat within a certain window of time.

In January, Wright began her weight-loss journey through intermittent fasting. It’s a time-restricted eating method where you only allow yourself to eat within a certain window of time. Wright says the method helped her lose 65 pounds so far.

“I just prayed and asked that [God] could see me through this journey, and could be consistent and be patient, because I feel that patience is key when it comes to weight loss ,” recalls Wright.

https://www.instagram.com/p/BlTTxDUBJ7E

How it works

Research suggests that weight loss is impacted by when we eat as much as by what we eat, which means intermittent fasting may help spur metabolism. There are several different methods for intermittent fasting, some of which are more restrictive than others. Wright recommends starting out with a less restrictive regime until your body is accustomed to it.

Wright began intermittent fasting with the 16:8 method, which required her to eat within an 8-hour window and fast for 16 hours. She cut out breakfast , she says, and ate just two meals a day — the first at 12 p.m., and the last meal around 8 p.m.

“I was only eating lunch and dinner, and it’s meant for you not to snack too,” Wright explains.

She says she stuck to low-carb meals , and limited her calories to between 1,800 and 2,000 calories a day. She tracked her calories on the MyFitnessPal app.

Health How one man lost 50 pounds using the 5:2 intermittent fasting diet

Other intermittent fasting diets take a different approach. The 5:2 method, for example, requires you to eat as you normally would for five days a week, but on two nonconsecutive days, you eat just one meal a day. Wright says she spent five months conditioning her body to the 16:8 method. At that point, she says, she switched to the 20:4 method. According to this method, you fast for 20 hours and have a 4-hour eating window.

“I wanted a change,” says Wright. “I wanted to try to boost my weight loss even more.”

Wright says you should be cautious about using a more restrictive method like the 20:4. Condition your body on a less restrictive method for an extended period first, she says. Since the window of time for eating on the 20:4 method is small, Wright says you should be careful to space your meals apart and not eat all your calories in one sitting.

“I’ll maybe take like 30 minutes to digest some of that food,” she says, “and then I’ll go and eat the rest.”

Make sure you eat healthy

One thing Wright enjoys most about intermittent fasting is that you decide what kind of foods you want to eat (she prefers a low-carb diet). But she warns against junk food .

“It’s definitely important to eat nutritious food when you’re on the diet,” she says. “I feel like if I was doing intermittent fasting just eating pizza and burgers and fries , I feel like I wouldn’t have had the amount of success I have right now.”

She says it’s important to consume all the macros your body needs — proteins, fats and carbs — and to have nutritiously diverse meals

“I’ll have egg whites and spinach, and I’ll have some carrots fruit on the side ... [or] I’ll have maybe a chicken breast with some quinoa on the side,” Wright says.

Allow yourself up to three cheat meals a month

Fasting for long periods of time can become tedious. That’s why Wright lets herself have three cheat meals a month. Whether it’s nachos, Chinese food or a Subway sandwich, cheat meals help her stay balanced, she says. But she warns not to overdo it.

“Once I’m done with my cheat meal I move on,” says Wright.

Exercise consistently

Wright incorporates exercise into her weight loss routine, working out out six days a week. Since she had a lot of weight to lose in the beginning, she was careful not to push herself too hard at first — just a brisk 15-minute walk on the treadmill each day .

“But as I got more comfortable with walking on the treadmill, I upped my time and I upped my speed and my incline,” she says.

After seven months, Wright now walks on the treadmill about 45 minutes a day. She includes high inclines and keeps at “a really brisk [pace].” Afterwards, she does about 30 minutes of high-intensity interval training .

Intermittent fasting teaches discipline

Wright says intermittent fasting is effective because it taught her self control. Since the rule required her to stop eating at 8 p.m., it prevented her from snacking before bed .

“It helped me not to go into the kitchen at night and eat cake or ice cream very late in the night,” says Wright. “And I feel like that is why it works, because it teaches you discipline when it comes to what time you’re eating your food.”

When you are intermittent fasting, Wright explains, it’s easy to become obsessive about timing your meals. She says it’s important to not be too fixated on time.

“Don’t be so tedious with time if that makes sense,” says Wright. “Like, it’s okay to be a couple of minutes off — like 10, 15 minutes off. That’s okay.”

Be consistent and stay patient

The key to being successful with intermittent fasting is to be consistent and not to lose patience, advises Wright.

“I feel like consistency is key," she says. "In order for you to see [a difference] you have to be consistent.”

She says it took her many years to get to 337 lbs, so it’s important to understand that losing the weight will also take a long time. At 272 lbs, Wright’s weight loss journey isn’t over. But she says she can do things now that she wasn’t able to do before — like cross her legs when she sits and get down on the floor to play with her daughter.

She says it feels “amazing.”

“This weight loss is such a blessing, and I’m so excited to see where this journey is going to take me,” Wright says. Her goal is to lose 100 pounds by the year’s end.

How to lose weight with intermittent fasting

• How it works: Intermittent fasting requires you to eat within a certain window of time and fast during the rest. There are several different methods for intermittent fasting, some of which are more restrictive than others. The 16:8 method, for example, requires you to eat within an 8-hour window and fast for 16 hours. You would only eat two meals a day, for example, your first meal starting at noon and your last around 8 p.m.
• Make sure you choose healthy foods. Eating healthy food is important when you are on an intermittent fasting diet. Make sure you are getting all the macros you need - fat, protein, and carbs, and eat nutritiously diverse meals.
• Allow yourself some cheat meals. Intermittent fasting can become tedious over a long period of time. Allow yourself to have up to three cheat meals a month, but be careful not to overdo it.
• Exercise consistently: Exercise will help boost your metabolism to lose weight. Depending on how much weight you need to lose, pick a routine that works for you.
• Intermittent fasting teaches discipline. Because you cannot eat once your fasting period begins, intermittent fasting will prevent you from snacking and will train you to be disciplined around food.
• Be consistent and stay patient. If you have a lot of weight to lose, keep in mind that you will not lose it over night. Consistency and patience are key.

MORE WEIGHT-LOSS SUCCESS STORIES (AND TIPS TO BORROW)

• How a spreadsheet helped this man lose 60 pounds
• These two economists used 'meta rules' to drop 120 pounds
• This man lost 50 pounds with intermittent fasting
• The 80/20 rule helped this woman lose weight
• Changing the way she talks about food helped this woman drop 10 pounds

Want more tips like these? NBC News BETTER is obsessed with finding easier, healthier and smarter ways to live. Sign up for our newsletter and follow us on Facebook , Twitter and Instagram .

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Boost Your Health and Wallet: The Power of Intermittent Fasting

Intermittent fasting may seem challenging, but with practice, you can get used to it and experience both the health and financial benefits.

You've probably heard about  intermittent fasting , since it's arguably one of the hottest health trends from the last couple of years. It's been heralded as not only a foolproof weight-loss method, but also as a potential cure for conditions like high cholesterol, high blood pressure, poor sleep, insulin resistance, cancer and Alzheimer's disease. A  2019 study in The New England Journal of Medicine  specifically connects intermittent fasting to "increased stress resistance, increased longevity and a decreased incidence of diseases, including cancer and obesity."

Want to learn more and perhaps try intermittent fasting yourself? Here's everything you need to know, including some of my own experiences with it. If you want to try it out for yourself, you should always consult a doctor before changing your diet or eating behaviors.

Read more:  Is Intermittent Fasting Actually Dangerous? How to Know If Time-Restricted Eating Is for You

What is intermittent fasting?

Most of us eat throughout the day, starting with breakfast when we wake up and perhaps ending with a dessert after dinner. If you have breakfast at 7 a.m. and a final treat at 8 p.m., you're consuming food for 13 hours; that's your current "eating window." The idea behind IF is simply to shorten that window -- not necessarily to eat less (though of course that's part of it), but to eat less often.

A common intermittent fasting plan includes an 8-hour eating window , meaning a 16-hour fast. So you could have lunch at noon and still finish your snack by 8 p.m. That's it. If you can stick to that, it may be enough to produce results.

But wait, isn't that just skipping breakfast? Haven't we heard for years that skipping breakfast actually leads to weight gain ? Yes, and yes. However, IF requires a "clean" fast to be effective (more on that below), and once you get accustomed to it, your appetite should correct so that you no longer overeat once your window opens.

Here's what I love about this: It costs nothing. It requires nothing. You don't have to buy books or gear or supplements or meals. You just adapt yourself to a slightly different way of eating (or "WOE," unfortunate though that sounds) and that's it. The simplicity -- and affordability -- of IF is what drew me to it.

Read more:  Best Meal Delivery Services of 2024

The best part about intermittent fasting

Gin Stephens is the author of Delay, Don't Deny: Living an Intermittent Fasting Lifestyle . Those first three words of the book title are the key to what makes this WOE worthwhile: You're not denying yourself anything, you're merely delaying it. You don't have to give up pizza because of the carbs or ice cream because of the sugar. You just have to wait until your window opens; then you can eat what you want. No, not the entire pizza or a whole pint of ice cream; you still have to be reasonable. But there are no exclusions, and that's incredibly liberating.

Think about nearly every other diet in history: Atkins , South Beach, paleo , keto . They all require you to cut out certain food groups entirely (fat, carbs, sugar) or eat excess food types (protein, cabbage soup). The reason these diets typically fail is they're not sustainable.

Stephens is fond of the saying: "Diets are easy in contemplation and hard in execution. Fasting is hard in contemplation but easy in execution." She comments further, stating, "I absolutely love that quote because it's so true. We've all started a new diet and we're all in . Then, as the days go by, the diet gets harder and harder to stick to. Intermittent fasting is the exact opposite. Instead of getting harder and harder, it gets easier and easier."

The intermittent fasting benefits no one talks about

Lost amid the talk of intermittent fasting's health benefits is a very real secondary perk: saving money. When you cut your diet down to one or two meals per day, your food costs drop accordingly. It's impossible to say exactly how much you stand to save because it depends on how often you dine out, what you buy at the grocery store and so on. 

However, even if your total food expenses drop by just 25%, that's a  huge  difference. Suppose you typically spend $100 per week on food. If you subtract the cost of seven meals per week, that might lower your weekly food expense to $70. Over the course of one month, you'd save $120, and over one year, $1,440.

That's a vacation or a down payment on a new car. Plus, there's a bigger-picture benefit as well: You're lowering your impact on the environment. Imagine if entire populations switched to two meals a day from three. We could get by on fewer crops and animals, which in turn would reduce overall water consumption. Maybe that's a bit of pie-in-the-sky thinking, but there's truth to it.

Read more:  The Most Environmentally Friendly Meal Kit Is Also the Best

I mention all this because after I started IF, I noticed I was spending less on food. Then, I started thinking about the external benefits of less food consumption, which made me feel even better about it. Eat less, help the planet. Win-win!

You might have to give up late-night snacking with IF.

How to start intermittent fasting

There are multiple schools of thought regarding how to schedule intermittent fasting. The Fast Diet is fairly different from what's described above; it's commonly known as 5:2, meaning you eat normally five days a week and fast for two. That may work for some, but two days of restricted eating doesn't sound very appealing. 

I prefer the daily method: Fast for at least 16 hours per day. The aforementioned New England Journal of Medicine study was based on an 18:6 structure: 18-hour fast, 6-hour eating window.

"16:8 is a great place to start," Stephens says, "but it may not be a weight-loss window for many people. That's because fat-burning ramps up between hours 18 and 24 of the fast. 19:5 was a great weight-loss sweet spot for me, and I lost about a pound per week when doing it. With 19:5, you fast for 19 hours a day and have an eating window of 5 hours. Your sweet spot may be different from mine, of course. Maybe it will be 18:6 or 20:4." Experimentation is key, she adds.

Before you embark on this journey, I recommend reading CNET writer Caroline Roberts' guide to doing intermittent fasting safely .

If your eating window doesn't include breakfast, you can still drink coffee as long as it's black and unsweetened.

A clean intermittent fast

The most important part of the equation is not the length of the window; it's the fast itself, which must be entirely "clean," according to Stephens. That means water, coffee and tea only, with absolutely no added fat, artificial sweeteners or the like. No bone broth, no water with lemon, no flavored teas. No gum, no mints, nothing with calories, period. The goal is to deprive your body of anything that triggers insulin production, because an insulin-deprived body turns to fat stores for energy.

One of the toughest hurdles for many people is giving up cream and sugar in their coffee. I was always a sugar man; when I made the switch to black coffee, it sucked for maybe a week or so. Now I'm a convert; I actually like it better. 

Stephens can't stress enough the importance of following the clean-fast rule. "For anyone who has ever tried IF in the past but was not fasting clean, now you know why it was so hard for you. The clean fast is so much easier, I promise."

Intermittent fasting resources

Stephens has a new book -- Fast, Feast, Repeat: The Comprehensive Guide to Delay, Don't Deny Intermittent Fasting -- that offers "a deeper dive into the science" than her first one. In the meantime, she recommends two other titles: The Obesity Code  by Dr. Jason Fung and  AC: The Power of Appetite Correction  by Dr. Bert Herring. 

There's also a Facebook group,  Delay, Don't Deny: Intermittent Fasting Support , that's an offshoot of Stephens' first book. It boasts over 300,000 members who ask and answer questions, and share stories and encouragement. You'll also find many before-and-after photos illustrating exactly how effective IF has been for some.

But not for all. You'll also see posts along these lines: "I fasted clean for two months, ate one meal a day and didn't lose a single pound." Others will note that it took them six months before the scale started to budge. "It takes time," Stephens says. "We didn't become overweight and unhealthy overnight, and it takes time to reverse these health conditions. Once your body has begun healing, fat loss is more likely." How long that takes depends on various factors, including age, sex at birth, starting weight and more.

My experience with intermittent fasting

I started IF in August 2018. At the time, I weighed around 181 pounds, which is acceptable for a 6-foot male. But I'd been 175 pounds for years, and suddenly it seemed I couldn't control my eating. I didn't like where my belly was headed.

After about two months, when my fasting windows varied (but averaged around 17:7), I'd lost 10 pounds. Needless to say, I was pleased with that result and became pretty evangelical about intermittent fasting. My excitement stemmed from not only the weight loss, but also the total lack of hardship. This didn't feel like a diet; it felt like a smart way to live. 

In fact, I discovered that I really liked this way of eating. When I was feeling a little hungry in the late morning? Just wait a bit longer, I told myself, your window opens soon. Then I'd busy myself with something and forget about it. And if I wanted a snack after 7 p.m.? Too bad, the window's closed for the day -- but you can have it tomorrow.

I stuck with intermittent fasting for about 10 months, though I'll admit I got frustrated at times. For one thing, I'd been hoping to lose another 5-10 pounds, and assumed they'd come off as easily as the first 10, but the scale held firm at 171.

Meanwhile, there were times when it was much harder to manage my window, like during family vacations when we'd all eat later than usual and breakfast was a part of the experience. Then came the holidays, various parties and family gatherings, which also presented window-related challenges. With a little planning, it's possible to adjust to these things, but ultimately I just got lazy about it -- probably because I'd lost the weight I'd initially wanted to lose.

Over the summer, I decided to pump the brakes. However, six months later, the scale once again showed 180. (Actually, 182 this time.) So in January 2020, I went back to IF, and once again, I'm really liking the simple discipline. I now do 18 hours on average. When I get to around 16 hours and start to feel a little tired or hungry, I hop on the elliptical or go for a run. By the time I'm done, showered and have made myself lunch, it's no trouble hitting 18 hours. Sometimes I stretch my fasting to 19 or even 20 hours.

Result: After four months (almost to the day), the scale shows 171. (One piece of advice, though: Stay off the scale. Weigh yourself once a month, tops. Otherwise, that thing will drive you nuts because weight fluctuates.) In the interim, I've eaten an almost embarrassing amount of food while my window was open. I don't have a sugar monkey on my back; I have a sugar gorilla. Nevertheless, I'm thinner and will see if I can hit 165 pounds. This lifestyle -- not diet, mind you -- is a piece of cake. Speaking of which, I think I'll go have one of those.

Whether you're fed up with diets or just want to improve your overall health, intermittent fasting is absolutely worth a try. It costs nothing to do and can actually save you money while maybe even helping the planet.

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Intermittent fasting might not be better than counting calories. Here’s why it still could work for you.

FILE - A dish with roast turkey breast is photographed in Concord, N.H., on Sept. 28, 2015. (AP Photo/Matthew Mead, File)

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As weight-loss plans go, it’s easy to see the allure of intermittent fasting: Eat what you want, but only during certain windows of time — often just eight hours a day.

Instead of counting calories or measuring portions, dieters just have to pay attention to the clock, said Courtney Peterson, a nutrition researcher at the University of Alabama at Birmingham.

“You have this really simple rule: Eat or don’t eat,” Peterson said.

The technique has skyrocketed in popularity in recent years, becoming a leading trending topic on social media.

But does time-restricted eating, a form of intermittent fasting, really help people shed pounds and boost health?

Here’s what you need to know about the practice:

WHAT IS INTERMITTENT FASTING?

Intermittent fasting is a meal strategy where people switch between fasting and eating on a regular schedule, defined as at least 14 hours with no food, Peterson said. That can mean variations such as eating every other day, eating five days a week and then fasting for two days or limiting daily eating to certain hours.

Time-restricted eating, where people condense all of their eating into a daily window of 10 hours or less, is the most popular form of intermittent fasting. Diners will delay breakfast until 10 a.m. or noon and then eat dinner by 6 p.m. or 8 p.m., forgoing food the rest of the time.

HOW IS IT SUPPOSED TO HELP?

The theory behind time-restricted eating is that it supports the circadian rhythm, or the body’s internal clock. Spending more time in a fasting state may boost the body’s processes that govern blood sugar and fat metabolism, for instance, scientists say.

Early studies in mice starting in 2012 seemed to show health benefits from time-restricted eating. Small studies in people with obesity suggested that the practice might help them lose weight and improve other health markers.

IS TIME-RESTRICTED EATING EFFECTIVE FOR WEIGHT LOSS?

Research has shown that people on time-restricted eating plans tend to eat fewer calories, which could explain weight loss.

Results from combined studies suggested that adults with obesity who limited their eating hours without focusing on calories naturally reduced their energy intake by 200 to 550 calories a day, losing 3% to 5% of their baseline body weight.

But a larger study of people observed over a longer period of time showed that the time restrictions alone might not matter.

A 2022 study published in the New England Journal of Medicine tracked 139 people with obesity for a year. Participants either followed a calorie-restricted diet during a certain time window or ate the same number of calories throughout the day. Both groups lost weight — 14 to 18 pounds on average — but there was no significant difference between the strategies.

“Our data right now suggests that time-restricted eating isn’t any better or worse than cutting calories,” Peterson said. Nor does the technique help burn more calories, she added.

Still, Peterson said, the simplicity of time restriction might be easier to maintain than a typical diet.

“Almost no one likes calorie counting,” she said.

IS INTERMITTENT FASTING SAFE?

Early clinical trials with eating windows of six to 10 hours found that time-restricted eating was “generally safe,” researchers reported in the journal Obesity .

But headline-grabbing research presented this year at an American Heart Association scientific session suggested that people following an 8-hour time-restricted diet had a much higher risk of death from cardiovascular disease than those who ate over 12 to 16 hours.

That research hasn’t been published in a peer-reviewed journal, noted Dr. Francisco Lopez-Jimenez, of the Mayo Clinic.

But he said there is reason to be cautious. Longstanding evidence suggests that skipping breakfast may be linked to cardiovascular disease and death. People should check with their health care providers before they try restricted eating, especially if the fasting window lasts until midday.

“It’s a call for pausing before you just recommend a particular diet,” Lopez-Jimenez said.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

The fasting diets Dr Michael Mosley was best known for

He changed the industry

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Known as the face of intermittent fasting, Dr Michael Mosley spent decades making science and medicine more accessible to the everyday person. Here’s why the world will remember Dr Mosley’s positive impact on the health industry and ‘diet culture’.  

This week the world mourns one of the health industry's most beloved members, Dr Michael Mosley. 

Known across the world for popularising the health benefits of intermittent fasting , Dr Mosley happened upon the divisive health trend after being diagnosed with type 2 diabetes in 2012.

Enlisting the expertise and scientific research of some of the UK’s top minds, Dr Mosley set out to prove the power of intermittent fasting – not only as a way to manage his diabetes diagnosis but as an effective weight loss method.

And prove it he did.

Whether you’re familiar with his name or not, Dr Mosley’s impact on the diet and weight loss industries is undeniable. 

A regular on the BBC, appearing on science and health programs for the past few decades, the doctor-turned-tv personality shared his health journey with millions of viewers. 

Publishing The Fast Diet in 2013 with author Mimi Spencer, Dr Mosley’s book became an instant bestseller, catapulting the 5:2 diet into the global spotlight. The dieting theory was refined even further in 2018, with Dr Mosley publishing The Fast 800, a weight loss-focused approach to sustained fasting. 

Both the 5:2 diet and the Fast 800 were designed to empower people with the tools and knowledge required to achieve a long-term health transformation, not just to drop a quick few kilos. So, how exactly do the diets Dr Mosley so publicly praised work?

The 5:2 diet

The leading method in the intermittent fasting field, the 5:2 diet was designed to encourage gradual weight loss and to improve an individual’s metabolic health.

Given the spaced-out structure and flexibility of the diet, many find the method far easier to stick to in the long term than alternative diets focussed on calorie restriction. 

As the name suggests, the diet allows routine eating for five days of the week, while the remaining two are restricted to 500 to 600 calories per day. Since the two fasting days carry most of the load when it comes to retraining the metabolism, there are no strict guidelines around what you can or cannot eat during the five routine days. 

The fasting days are also entirely up to the individual – as long as they aren't consecutive – making the 5:2 diet’s flexibility far easier to incorporate into any lifestyle or routine.

Most people who regularly engage in the 5:2 method find a little bit of planning is required to ensure the fast days don’t leave them feeling entirely depleted. With the fast days’ calorie intake limited to 500 calories for women and 600 calories for men, it is recommended people opt for small meals that are high in fibre and protein. 

Lastly, sticking to the strict calorie intake on the two fast days is unlikely to be beneficial if you spend the remaining five days bingeing on junk food and highly processed, calorie-dense meals. 

The Fast 800 

Taking the methodology a step further, Dr Mosley popularised the Fast 800 method as a continuation of the 5:2 diet. Following the principles of a low-carb Mediterranean-style diet, the Fast 800 was designed to kickstart significant weight loss and reset one’s metabolism. 

Like the 5:2 method, the crux of this weight loss technique is in the name. Participants are instructed to consume only 800 calories per day for a minimum of two and a maximum of 12 weeks. To completely experience the weight loss benefits of this sustained fasting method, regular exercise is encouraged, as well as incorporating time-restricted eating. 

As we know, if we eat more calories than we burn off through exercise each day, the excess is stored as fat. The Fast 800 diet uses prolonged fasting and lowered intake of carbohydrates to encourage the body to take fat from your fat stores to burn as fuel. 

More Coverage

Dr Mosley famously presented a series in 2021 called Lose a Stone in 21 Days, in which individuals dropped up to 6.4kg in only three weeks using the Fast 800 method. 

At their core, the 5:2 and Fast 800 diets were designed to promote an all-round healthier lifestyle, with Dr Mosley himself demonstrating the benefits. For individuals who have struggled with disordered eating in the past, suffer from type 1 diabetes or another active medical condition, or are pregnant or breastfeeding, these fasting methods are not recommended. 

Of course, with any fasting or intermittent fasting method, it is always important to consult your healthcare professional before embarking on a new diet to ensure any medical concerns and nutritional benchmarks are able to be met. 

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Experts weigh in

Intermittent fasting and weight loss: Systematic review

Affiliations.

• 1 Researcher for the Anishinaabe Bimaadiziwin Research Program in Sioux Lookout, Ont.
• 2 Family physician practising at the Sioux Lookout Meno Ya Win Health Centre and Assistant Professor in the Division of Clinical Sciences at the Northern Ontario School of Medicine.
• 3 Assistant Professor in the Division of Clinical Sciences at the Northern Ontario School of Medicine in Sioux Lookout.
• 4 Research assistant in the Anishinaabe Bimaadiziwin Research Program.
• 5 Primary care nurse at the Hugh Allan Clinic in Sioux Lookout.
• 6 Associate Professor in the Division of Clinical Sciences at the Northern Ontario School of Medicine in Sioux Lookout.
• 7 Research consultant for the Sioux Lookout Meno Ya Win Health Centre. [email protected].
• PMID: 32060194
• PMCID: PMC7021351

Abstract in English, French

Objective: To examine the evidence for intermittent fasting (IF), an alternative to calorie-restricted diets, in treating obesity, an important health concern in Canada with few effective office-based treatment strategies.

Data sources: A MEDLINE and EMBASE search from January 1, 2000, to July 1, 2019, yielded 1200 results using the key words fasting, time restricted feeding, meal skipping, alternate day fasting, intermittent fasting, and reduced meal frequency .

Study selection: Forty-one articles describing 27 trials addressed weight loss in overweight and obese patients: 18 small randomized controlled trials (level I evidence) and 9 trials comparing weight after IF to baseline weight with no control group (level II evidence). Studies were often of short duration (2 to 26 weeks) with low enrolment (10 to 244 participants); 2 were of 1-year duration. Protocols varied, with only 5 studies including patients with type 2 diabetes.

Synthesis: All 27 IF trials found weight loss of 0.8% to 13.0% of baseline weight with no serious adverse events. Twelve studies comparing IF to calorie restriction found equivalent results. The 5 studies that included patients with type 2 diabetes documented improved glycemic control.

Conclusion: Intermittent fasting shows promise for the treatment of obesity. To date, the studies have been small and of short duration. Longer-term research is needed to understand the sustainable role IF can play in weight loss.

Objectif: Examiner les données probantes concernant le jeûne intermittent (JI) comme solution de rechange aux régimes faibles en calories dans le traitement de l’obésité, une importante préoccupation en matière de santé au Canada, compte tenu de la rareté des stratégies thérapeutiques efficaces applicables en clinique.

Sources des données: Une recherche documentaire effectuée dans MEDLINE et EMBASE, du 1 er janvier 2000 au 1 er juillet 2019, a produit 1200 résultats à l’aide des expressions clés suivantes : fasting, time restricted feeding, meal skipping, alternate day fasting, intermittent fasting et reduced meal frequency .

Sélection des études: Quelque 41 articles décrivant 27 études portaient sur la perte de poids chez les patients en surpoids et obèses : 18 petites études randomisées contrôlées (données probantes de niveau I) et 9 études comparant le poids après un JI avec le poids au point de départ et sans groupe témoin (données probantes de niveau II). Les études étaient souvent de courte durée (de 2 à 26 semaines), et la participation était peu nombreuse (de 10 à 244 sujets) ; 2 études ont duré 1 an. Les protocoles variaient, et seulement 5 études incluaient des patients atteints de diabète de type 2.

Synthèse: Dans les 27 études sur le JI, une perte pondérale variant de 0,8 à 13 % s’est produite sans événements indésirables sérieux. Douze études comparant le JI et la restriction de calories ont fait valoir des résultats équivalents. Les 5 études qui comptaient des patients atteints de diabète de type 2 ont documenté un meilleur contrôle glycémique.

Conclusion: Le jeûne intermittent semble prometteur pour le traitement de l’obésité. Jusqu’à présent, les études comptaient peu de sujets et étaient de courte durée. Des recherches à plus long terme sont nécessaires pour comprendre le rôle durable que peut jouer le JI dans la perte pondérale.

Copyright© the College of Family Physicians of Canada.

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Study: Intermittent Fasting and High-Intensity Exercise Produce Better Weight Management Results When Combined

• A new study suggests that combining time-restricted eating and high-intensity functional training may provide better results for women with obesity compared to practicing the methods on their own.
• Women with obesity who did both TRE and HIFT saw the best results when it came to weight management and cardiometabolic health markers.
• Practicing the strategies together may help burn extra fat while also building lean muscle.

Combining time-restricted eating and high-intensity functional training may boost metabolic health and weight loss more than each method alone, new research suggests.

A study published May 1 in the journal PLOS One found that inactive women with obesity who practiced not just one but both strategies had more significant reductions in body composition and lipid and glucose levels.

Time-restricted eating (TRE), a type of intermittent fasting , refers to narrowing food intake to specific windows of the day, while high-intensity functional training—or HIFT—involves aerobic and resistance exercises that mimic everyday movements, such as pulling or lifting, performed at a rapid pace. Both strategies have become popular in recent years.

“We can highlight in this study that TRE is a good solution to combat obesity, easy to implement since it does not require people to limit their overall food intake or count the total number of daily calories,” study author Rami Maaloul, PhD, of the University of Sfax, Tunisia, said in an interview published by PLOS One . “For optimal benefits, you should incorporate both TRE and HIFT into your strategy.”

The Good Brigade / Getty Images

A Closer Look at the Findings

According to the authors, previous research has suggested that practicing TRE or HIFT alone in the “short term” may help people lose weight and improve markers of cardiometabolic health, such as blood pressure and glucose levels.

Researchers wanted to investigate whether combining TRE and HIFT would yield even more significant health benefits.

The team recruited 64 women with obesity; the average age was 32. Researchers assigned the participants to practice either time-restricted eating only, high-intensity functional training only, or a combination of the two. 

The women who followed the time-restricted eating regimen ate only between 8 a.m. and 4 p.m. Those in the other groups exercised three days a week with an instructor. 

After 12 weeks, participants in all three groups showed significant weight loss, waist and hip circumference reductions, and positive changes in lipid and glucose levels. The people who exercised also had lower blood pressure .

Those practicing both TRE and HIFT, however, saw more pronounced benefits in general than those in the other groups.

“This study highlights another exciting positive effect of intermittent fasting, which is to augment the positive effects of exercise on metabolic health,” Julie Pendergast, PhD , an associate professor of biology at the University of Kentucky who researches metabolism, told Health .

Weaknesses in the Research

The authors acknowledged several limitations, including the small sample size, the specificity of the functional exercises, and the fact that eating habits were self-reported and not measured objectively. 

Additionally, people who practiced TRE also reported consuming fewer calories, so it's unclear whether the health benefits resulted from a shift in eating times or reduced caloric intake. Some previous research has suggested that any benefits seen during TRE may in fact be due to fewer calories consumed in light of the shorter eating window.

The study didn’t explore that question or why people who did both HIFT and TRE had the best outcomes. However, experts said a couple of factors may be at play.

According to Pendergast, “both interventions result in a metabolic shift to promote fat burning by the body.” 

Exercise also builds lean muscle, she added.

“I think the key message from this study is incorporating physical activity and training in the setting of active weight loss can be beneficial towards the maintenance of lean tissue, which is invariably lost to a degree when someone’s losing weight,” Sean Heffron, MD , a cardiologist at the Center for the Prevention of Cardiovascular Disease at NYU Langone Heart, told Health .

What to Consider Before Practicing TRE and HIFT

If you want to begin a new exercise or diet regimen, it’s best to consult with a healthcare provider first.

Maaloul said people interested in starting a HIFT routine may want to begin slowly and work their way up to a higher intensity. Doing too much too soon may cause injury.

While Pendergast said that “when practiced carefully, studies have shown [that TRE] is safe and effective,” the eating plan may not be ideal for some people, including those with diabetes or a history of eating disorders, or people who are pregnant or suspect they are pregnant.

Experts say it’s also important to focus on what—not just when—you’re eating. Restricting eating to certain hours wouldn’t negate the health effects of adopting a poor diet. 

And to lose weight and remain healthy long-term, Heffron said to consider creating habits you can maintain. That means that if you don’t enjoy intermittent fasting or high-intensity functional exercise—or find them too challenging to stick to—they may not be the best approaches for you.

Ameur R, Maaloul R, Tagougui S, et al. Unlocking the power of synergy: high-intensity functional training and early time-restricted eating for transformative changes in body composition and cardiometabolic health in inactive women with obesity . PLOS One . 2024;19(5):e0301369. doi:10.1371/journal.pone.0301369

PLOS One . Interview with Rami Maaloul of the University of Sfax, Tunisia .

Related Articles

Intermittent Fasting vs. Calorie Counting: Which Is More Effective for Weight Loss?

• When compared, time-restricted eating (also known as intermittent fasting) and calorie counting result in similar weight loss, new research shows.
• The success of the two weight loss strategies may come down to one common thread: fewer calories consumed throughout a 24-hour period.
• Ultimately, experts say the best strategy for weight loss is the program that is most sustainable for the specific person.

New research comparing time-restricted eating (also known as TRE, intermittent fasting , or IF) to calorie counting shows that the two weight loss strategies produce similar results in a racially diverse population of adults with obesity.

Since intermittent fasting gained attention a couple of years ago as a way to lose weight, experts and dieters alike have debated whether this strategy is more or less effective than simple calorie counting. Some have argued that restricting eating to specific windows of the day naturally leads to successful weight loss, while others believe monitoring daily calories is a more effective path.

As it turns out, one might not be better at the job than the other.

While previous studies have examined the effects of combining calorie counting with intermittent fasting, this new research—published June 27 in Annals of Internal Medicine —is one of the first to look at these strategies in isolation.

Given that intermittent fasting is often simpler and easier for dieters than tracking every calorie in every bite throughout the day, the researchers wanted to see if it was also more effective, said Shuhao Lin, MS, RDN, the study’s primary researcher and a registered dietician with the University of Illinois Chicago.

If you’re weighing the merits of intermittent fasting vs. calorie counting for weight loss, here’s what to know.

How Researchers Compared the Two Weight Loss Strategies

For the study, Lin and her colleagues at the University of Illinois Chicago recruited 90 adults with obesity. Participants had an average age of 40; 33% were Black, and 46% were Hispanic.

The researchers divided the participants into three groups: one could eat only between noon and 8:00 PM, one restricted their regular daily caloric intake by 25%, and another made no dietary changes. Seventy-seven participants ended up completing the study.

After 12 months, the intermittent fasters and the calorie counters had surprisingly similar weight loss results. “In our study, we found that by shortening the eating window to eight hours, people reduced the same amount of calories intake as counting calories—around 400 kcal per day in both groups,” Lin said.

Both groups lost about 5% of their body weight.

Although intermittent fasting and calorie counting achieved neck-and-neck weight loss results, the same wasn’t true for another facet of health: blood sugar management. People in the 8-hour time-restricted eating group had improved insulin sensitivity, meaning their bodies got better at regulating blood sugar.

However, Lin said this may be because people in this group started with worse insulin sensitivity than participants in other groups, allowing more room for improvement. “Nonetheless, it shows the potential of time-restricted eating to improve insulin sensitivity in adults with impaired insulin sensitivity at baseline,” she said. “More research is needed to investigate how time-restricted eating may help people with impaired insulin sensitivity and type 2 diabetes.”

It’s important to note that the study’s results regarding weight loss may not apply when comparing the two approaches for a longer stretch of time. A study published in January 2023 in the Journal of the American Heart Association found that after six years, participants who restricted calories lost more weight than those who continued an intermittent fasting diet. Intermittent fasters who consumed medium- or large-sized meals during their daily window of eating were especially likely to gain weight over time.

Related: Could Calorie Restriction Slow Aging? New Research Shows a Link—But Experts Have Concerns

Why Intermittent Fasting and Calorie Counting May Be Comparable

“All diets work” has become a rallying cry among many weight loss specialists who believe that sticking to any energy reduction plan will likely help with weight loss. But intermittent fasting and calorie counting are quite different processes, so how do they achieve similar results?

“Since IF is shortening your eating window, you’ll likely consume fewer calories during that window by default,” Melissa Mitri, MS, RDN , weight loss expert and owner of Melissa Mitri Nutrition, told Health . “Additionally, IF can prevent late-night snacking and reduces your appetite throughout the day.” 

Certain practices can make intermittent fasting and calorie counting more successful. “For IF to be effective for weight loss, you want to focus on the overall quality of your diet. Even though there are technically no ‘rules’ on what you can or can’t eat on IF, prioritizing nutritious whole foods lower in calories and fat will bring the best results,” Mitri said.

As for calorie counting, it can help to remember that not all calories are created equal. Some, such as those from complex carbohydrates and fiber, will likely provide more satiety, keeping you fuller throughout the day.

Choosing a Weight Loss Plan That Works for You

Choosing a diet for weight loss is a highly personal decision. If you’re choosing between intermittent fasting and calorie counting, you may want to assess your personal preferences, habits, and tendencies.

“If you don’t enjoy counting calories and using a food log app, then IF may be better for you,” Mitri said. “However, if your schedule doesn’t allow you to shorten your eating window easily, or you find yourself hungry when you go too long without eating, then calorie counting may be a better option.”

Regardless of which diet you opt for, don’t forget that weight loss alone isn’t an indicator that an eating plan is healthy and nutritious. “Whether you choose IF or calorie reduction for weight loss, it’s always important to prioritize a balanced diet,” Mitri said. Exercise will also offer enormous health benefits and burn additional calories, inching you toward your weight loss goal.

Related: What Is a Calorie Deficit—And How Do You Reach It?

Lingering Questions About Intermittent Fasting

Research into the effectiveness of intermittent fasting vs. calorie restriction is in the early stages, and future studies may reveal more about the advantages and disadvantages of the weight loss strategies. A larger study, for example, may help tease apart the merits of the two diets.

Lin said there are many additional research avenues to tackle regarding intermittent fasting specifically.

“I think the important next steps to research in this field is to expand the population we are studying,” she said. “For example, we need more research to see if time-restricted eating is safe and effective for people with type 2 diabetes, cancers, or other metabolic diseases."

"It would also be interesting to see research using intermittent fasting alongside other weight loss treatments, such as drug treatments, to improve or maintain weight loss," she added. "There are definitely many things we still have to explore in the field.”

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Start the clock!

Practicing protein pacing — evenly spacing protein consumption throughout the day — and intermittent fasting — limiting eating to certain times — is better for gut health, weight loss, and metabolic responses than just restricting calories, a new Arizona State University study finds .

27 women and 14 men who were overweight or obese were divided into two groups: one ate a heart-healthy, calorie-restricted diet, while the other followed a calorie-restricted plan incorporating intermittent fasting and protein pacing.

Both groups were monitored over eight weeks for changes in their weight, body composition, gut bacteria, and metabolic health.

Participants following the intermittent fasting and protein-pacing diet significantly reduced their gut symptoms, increased their beneficial gut bacteria, lost more weight, and shed more body fat.

The fasting/pacing group dropped an average of 8.81% of their initial body weight while those on the calorie-restricted diet lost just 5.4% on average. The calorie-restricted group also received worse news about their metabolic health.

As part of the findings, published last week in the journal Nature Communications , the researchers determined that the intermittent fasting protocol increases beneficial gut microbes tied to a lean body type and better health while raising the levels of proteins in the blood linked to weight loss.

“A healthy gut microbiome is essential for overall health, particularly in managing obesity and metabolic diseases,” said Karen Sweazea, the ASU principal study investigator.

“The gut bacteria influence how we store fat, balance glucose levels and respond to hormones that make us feel hungry or full,” she continued. “Disruptions in the gut microbiota can lead to increased inflammation, insulin resistance and weight gain, underscoring the critical role of gut health in preventing and managing metabolic disorders.”

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Never miss a story.

Intermittent fasting has been associated with weight loss, a lower risk of Type 2 diabetes and heart disease, less inflammation , and improved immune function. But research has also cast doubt on its purported benefits.

One recent major study found that those who limit their eating to a window less than eight hours a day are more likely to die from cardiovascular disease than people who eat over 12-16 hours a day. Medical experts also warn that intermittent fasting is not for everyone.

Consult your doctor if you have diabetes, kidney stones, gastroesophageal reflux, or other medical conditions before beginning an intermittent fasting plan.

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Dr Michael Mosley never expected to have diabetes. His mission to 'cure' his diagnosis put a global spotlight on intermittent fasting

It was a normal day in 2012 when Dr Michael Mosley made an appointment with his doctor.

The British television producer and presenter was worried about a possible melanoma on his skin that had been playing on his mind.

He rolled up his sleeve for a blood test before being sent away, left to wait for the results.

"Good news, your skin is fine," his doctor told him.

"Bad news, you've got type 2 diabetes."

The diagnosis would be the catalyst for a health journey that would bring Dr Mosley worldwide recognition, influencing the eating habits of millions and drawing criticism from other medical professionals.

Dr Mosley's body was found on the Greek island of Symi on Sunday local time, after he went missing last week while out for a walk alone during a holiday with his wife. 

Popularising intermittent fasting

Following his diabetes diagnosis, medication was instantly mentioned as the logical next step.

But Dr Mosley said, "no thanks".

"My dad had had type 2 diabetes and had died of complications, even though he was taking the medication," he said in an interview with The House of Wellness in 2020.

"So I thought, this is not a good way to go."

Dr Mosley had previously heard about intermittent fasting and immediately started researching.

"Like you, I thought it was crazy," he admitted.

His research led him to get in touch with neuroscientist Mark Mattson, who published a paper on the 5:2 diet with 15 other scientists the previous year.

The 5:2 diet is a type of intermittent fasting where calories are restricted for two days of the week, with normal calorie intake for the other five days of the week.

At this point, Dr Mosley had been working with the BBC for decades and had presented and produced a number of science programs.

He couldn't deny his diagnosis would make compelling viewing.

"I persuaded the editor of [BBC science program] Horizon … to commission a film to see if I could cure myself of diabetes through intermittent fasting," he said.

Dr Mosley had no inkling his experiment would work, but remained optimistic.

At the end of the program, Dr Mosley had lost 9kg and his blood sugars were "entirely fine."

The episode drew a surprisingly high audience of 3 million viewers, particularly as it aired during the London Olympics.

"I was absolutely astonished, I have to say," Dr Mosley said on reflection once the experiment was complete.

"And I didn't really understand it."

Diabetes 'in remission'

Dr Mosley has said, "at each stage, I've relied on other people's science".

In order to understand what just happened to his body, Dr Mosley got in touch with Professor Roy Taylor at Newcastle University.

"He said, basically it was a rapid weight loss that had led to the fat draining out of my liver and my pancreas," he said.

Dr Mosley said Professor Taylor had already demonstrated in a dozen patients that you could "put diabetes into remission".

"That's the word he uses. He doesn't like the word 'reverse' because reverse implies it's permanent and if you put the fat on again, then there's a good chance it will come back.

"He's the guy who explained the science to me, he had all the science behind him, he was one of the world's leading diabetes specialists … and no one believed him. All the other doctors said this was nonsense.

"He said, 'I'm seeing all these patients who are losing weight, their diabetes is going away — explain that.'"

The bestseller and the 'fasting frenzy'

Soon thereafter, Dr Mosley paired up with food and fashion writer Mimi Spencer to write The Fast Diet.

The book became a bestseller in the UK, with the New York Times saying Dr Mosley had "sent the British into a fasting frenzy."

Celebrity chef Hugh Fearnley-Whittingstall wrote in The Guardian that he felt "lean and sharp" on the diet, adding "I feel I might just be part of a health revolution".

But the book's success was not without its criticism.

Shortly after its publication, Britain's publicly funded National Health Service (NHS) put out a statement on its website.

"Despite its increasing popularity, there is a great deal of uncertainty about IF [intermittent fasting] with significant gaps in the evidence."

And while scientists had done plenty of research on the benefits of intermittent fasting on rats, there weren't many trials done on humans.

According to Diabetes Australia, intermittent fasting can be safely undertaken by someone with diabetes, but there are some considerations, including first speaking with your doctor beforehand.

"Studies are limited to a time frame and whether individuals can sustain intermittent fasting long-term is unclear," the Diabetes Australia website states.

Years later, in 2021, Dr Mosley would present a Channel 4 series called Lose a Stone in 21 Days.

The program claimed individuals could drop 1 stone (6.4kg) in 21 days by calorie restricting to 800 calories a day.

Beat, a UK charity supporting those affected by eating disorders, wrote that "the programme caused enough stress and anxiety to our beneficiaries that we extended our Helpline hours to support anyone affected and received 51 per cent more contact during that time".

From medicine to television

Born in Calcutta, India, Dr Mosley moved to England with his family when he was a child.

He studied philosophy at Oxford University before later moving into medicine with the intention to become a psychiatrist.

But in 1985, a disillusioned Dr Mosley joined a trainee assistant producer scheme at the BBC.

He produced a number of programs, including the 2004 series Inventions That Changed The World with then Top Gear presenter Jeremy Clarkson.

His influence also spanned to Australia.

In 2021, he presented the series Australia's Health Revolution for SBS, which was followed by Australia's Sleep Revolution three years later.

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