fbpx

Alternate Day Fasting: A Beginner’s Guide To Fasting Every Other Day

Discover the health benefits of the “Every Other Day Diet”.

Alternate day fasting (ADF) is a type of intermittent fasting that involves fasting every other day. It offers some of the same great health benefits of intermittent fasting with even more flexibility in some ways.

But, does alternate day fasting work for weight loss? Will fasting every other day improve body composition and health? What are the pros and cons of ADF fasting vs intermittent fasting with a daily fasting window?

In this guide, we will explain what alternate day fasting is, how to follow this diet approach, and what the benefits and effects of intermittent fasting are.

We will cover the following: 

Let’s dive in! 

A clock on an empty plate and a sticker that says fasting.

What Is Alternate Day Fasting?

Alternate day fasting, also called ADF fasting for short, is an approach to intermittent fasting diets that looks at the week on a macro scale rather than each individual day.

In the strictest sense, an alternate day fasting diet involves fasting every other day and then consuming what you want to eat, and when you want to eat it on the days you are not fasting (“feasting day”).

For example, if you are following an alternate day fasting diet for weight loss, you might eat normally on Monday, which means that you will try to eat a nutritious, well-balanced diet with regularly scheduled meals and snacks throughout the day. 

Then, the next day, on Tuesday, you would fast for 24 hours. 

On Wednesday, you would resume normal eating. 

On Thursday, you would do another 24-hour water fast with no food intake. 

This pattern would be continued throughout the week, alternating 24 hours fasting periods with eating days.

Given the structure of engaging in a fast every other day, an alternate day fasting diet is sometimes called the “The Every Other Day Diet,” which was coined by Dr. Krista Varady.

A person eating a bowl.

What Is Modified Alternate Day Fasting?

Although some people who follow the alternate day fasting diet do indeed fast every other day, abstaining from all caloric food and beverages, there are various versions of the alternate day fasting diet that still fall under the umbrella of ADF fasting.

For example, the most common version of alternate day fasting plans involves a modified fast every other day with some calorie intake allowed.

Instead of doing a strict 24-hour water fast every other day, dieters eat around 500 calories on the fasting day, choosing the specific foods and eating schedule that works best for them.

Eating only 500 calories per day is still well below the total daily energy expenditure or caloric requirements of both men and women.

This means you will still generate a significant caloric deficit when doing a modified fast with severe caloric restriction every other day rather than a full-on water fast.

The rationale is that this version makes ADF fasting more sustainable and approachable for people who cannot fathom water fasting every other day, from a practical or emotional standpoint.

There are other iterations and modifications of alternate day fasting that may require complete water fasting several days per week, but the frequency may not be exactly every other day. 

For example, you might follow your normal diet for two days and then fast every third day, though this isn’t technically alternate day fasting.

A person eating a bowl of fruit.

How to Follow An Alternate Day Fasting Diet

As described, the official alternate day fasting diet involves water fasting every other day and then following a normal diet on the non-fasting days.

So, what does this mean, fasting every other day?

Technically, when you are fasting, you are not supposed to consume any food or beverages that contain calories, complete calorie restriction. 

This means you can have unsweetened tea or herbal tea, seltzer or club soda, plain water, electrolyte tablets in your water as long as they are unsweetened, and black coffee.

If you want to follow a modified alternate day fasting diet plan, you may decide to alternate between following your normal diet one day and consuming 500 calories or 20 to 25% of your daily energy requirements on the “fasting days.”

Most evidence suggests that it doesn’t really matter when or how you split up your 500 calories on your caloric restriction fasting days. 1Hoddy, K. K., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., & Varady, K. A. (2014). Meal timing during alternate day fasting: Impact on body weight and cardiovascular disease risk in obese adults. Obesity22(12), n/a-n/a. https://doi.org/10.1002/oby.20909

A person eating granola and fruit.

Essentially, whether you choose to eat all of the calories in a single meal at lunchtime or dinner or spread evenly throughout the day, the physiological effects seem to be roughly equivalent.

In terms of what you can eat on your regular eating days when following an alternate day fasting diet, healthy, nutritious, calorie-sensible foods are optimal. 

Studies have not found that macronutrient ratio does not seem to affect how much fat you lose on an alternate day fasting plan.2Klempel, M. C., Kroeger, C. M., & Varady, K. A. (2013). Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet. Metabolism62(1), 137–143. https://doi.org/10.1016/j.metabol.2012.07.002

‌In other words, it seems that people lose the same amount of fat mass and total weight whether they follow a high-fat or low-fat diet on a fasting every-other-day plan.

Finally, as with any weight loss diet, it is highly encouraged to exercise regularly when fasting every other day for weight loss. 

Studies have found that those who combine exercise with an ADF fasting diet lose more weight than those who are not active.3S, B., Mc, K., Cm, K., Jf, T., & Ka, V. (2013, July 1). Alternate Day Fasting and Endurance Exercise Combine to Reduce Body Weight and Favorably Alter Plasma Lipids in Obese Humans. Obesity (Silver Spring, Md.). https://pubmed.ncbi.nlm.nih.gov/23408502/

‌Plus, physical activity provides additional health benefits and reduces the risk of lifestyle diseases, so it should be a mainstay in your health routine whether or not you are doing an intermittent fasting diet for weight loss, weight maintenance, or just improved health.

A person drinking a glass of water.

Benefits of Alternate Day Fasting

The “Every Other Day Diet” alternate-day fasting protocol has been studied fairly extensively.

In many ways, some of the same benefits of a time-bound intermittent fasting diet apply to alternate day fasting regimens, even those in which you don’t perform a strict water fast every other day but drop your calories way down to about 20 to 25% of your actual energy requirements.4Varady, K. A., Bhutani, S., Church, E. C., & Klempel, M. C. (2009). Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. The American Journal of Clinical Nutrition90(5), 1138–1143. https://doi.org/10.3945/ajcn.2009.28380

‌Furthermore, if you are actually fasting 24 hours every other day, there may be some additional benefit of alternate day fasting vs time-restricted intermittent fasting with periods of fasting and consolidated eating every 24 hours.

The reason that there may be additional alternate-day fasting diet benefits compared with regular intermittent fasting protocols is that some benefits of fasting are actually only realized with extended fasting. 

Depending on the particular intermittent fasting diet schedule you follow, you may not be fasting long enough to trigger some of the benefits of extended fasting. 

For example, with a 14/10 or 16/8 intermittent fasting diet, just fasting for 14 to 16 hours per day will certainly initiate some fasting benefits, but certain physiological effects of fasting work on a longer timeline. 

This means that once you start your eating window 14 to 16 hours after the fast begins, you will take yourself out of the fasted state and may not experience some of the benefits of 24-hour fasting.

A clock on an empty plate.

Here are some of the top benefits of alternate-day fasting diets:

#1: Alternate Day Fasting May Be Easier to Sustain

Some people find that one of the benefits of alternate day fasting vs intermittent fasting diet schedules with fasting and eating windows every day is that it is easier to stick with alternate day fasting. 

With some of the stricter intermittent fasting schedules, your eating window is quite small. 

This can make it difficult to fit in workouts, and it could be physically and emotionally uncomfortable to deal with hunger and energy restriction every single day. 

Plus, from a social perspective, you may have engagements with friends or celebratory occasions where you want to eat in the company of others. 

However, if you are following an intermittent fasting diet and the meal time for social interaction falls during your fasting window instead of your eating window, you will not be able to enjoy a meal with friends or loved ones. 

A snack box with hummus, chips and fruit.

In contrast, if you are following the ADF fasting pattern, it can be an easier mental hurdle to clear. 

You will know that every other day, you will have complete freedom to eat when you want to eat. This can make it easier to schedule more vigorous or long workouts, social events, etc.

However, it’s important to note that the psychology and logistics of eating, fasting, weight loss, and dieting are highly individualized.

You may find that there are benefits of fasting every other day vs intermittent fasting within a given window of time every single day based on how your own mind works and the logistics of your own life.

Research studies have found that long-term adherence to alternate-day fasting diets wherein calories are cut to just 25% of daily energy needs every other day do not result in better long-term adherence than moderate, daily caloric restriction diets like traditional calorie restriction diets.5Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936

Fruit and veg in a tupperware.

#2: ADF Dieting May Support Weight Loss

Studies have found that intermittent fasting can reduce body fat, improve body composition, and support overall weight loss getting you to your ideal, healthy weight.

However, while studies looking specifically at alternate day fasting protocols also confer weight loss and fat loss results, most evidence suggests that alternate day fasting does not improve weight loss or fat loss results relative to regular caloric restriction diets that involve cutting calories a modest amount every day.6Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936

Moreover, studies7Das, S. K., Gilhooly, C. H., Golden, J. K., Pittas, A. G., Fuss, P. J., Cheatham, R. A., Tyler, S., Tsay, M., McCrory, M. A., Lichtenstein, A. H., Dallal, G. E., Dutta, C., Bhapkar, M. V., DeLany, J. P., Saltzman, E., & Roberts, S. B. (2007). Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial. The American Journal of Clinical Nutrition85(4), 1023–1030. https://doi.org/10.1093/ajcn/85.4.1023 have not found that you will lose more belly fat (visceral fat), the type of harmful body fat strongly associated with obesity and impaired markers of health relative to regular daily caloric restriction diets.

#3: Alternate Day Fasting Diets May Control Hunger

The alternate day fasting results from clinical trials regarding how these diets affect hunger relative to traditional weight loss diets are mixed.

Some studies have found that people get used to fasting every other day and find that over time, their hunger on fasting days goes down, making fasting on alternate days easier than when starting the diet.8Klempel, M. C., Bhutani, S., Fitzgibbon, M., Freels, S., & Varady, K. A. (2010). Dietary and physical activity adaptations to alternate day modified fasting: implications for optimal weight loss. Nutrition Journal9(1). https://doi.org/10.1186/1475-2891-9-35

A plate clock.

Other studies have found that hunger levels remain unchanged with these forms of intermittent fasting.9Lk, H., Sr, S., Ck, M., Sd, A., & E, R. (2005, January 1). Alternate-day Fasting in Nonobese Subjects: Effects on Body Weight, Body Composition, and Energy Metabolism. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/15640462/

‌Although human studies are limited, animal studies suggest that fasting every other day does result in a reduction of ghrelin, the hunger hormone on fasting days, and an increase of leptin, the satiety hormone.10Varady, K. A., Hudak, C. S., & Hellerstein, M. K. (2009). Modified alternate-day fasting and cardioprotection: relation to adipose tissue dynamics and dietary fat intake. Metabolism58(6), 803–811. https://doi.org/10.1016/j.metabol.2009.01.018

‌These hormonal changes from fasting every other day may make it easier to sustain ADF fasting in the long term for better weight loss results.

Human studies have also found that alternate day fasting diets seem to increase levels of brain-derived neurotrophic factor (BDNF), which plays a role in energy balance and body weight.11Catenacci, V. A., Pan, Z., Ostendorf, D., Brannon, S., Gozansky, W. S., Mattson, M. P., Martin, B., MacLean, P. S., Melanson, E. L., & Troy Donahoo, W. (2016). A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity24(9), 1874–1883. https://doi.org/10.1002/oby.21581

‌Further studies are necessary to really examine how ADF eating patterns affect hunger, satiety, and the hormonal control of appetite and weight loss.

Evidence has found that modified ADF dieting by eating 500 calories on fasting days does seem to reduce hunger sensations and make it feel more tolerable from a physical and emotional standpoint.12Lk, H., Sr, S., Ck, M., Sd, A., & E, R. (2005, January 1). Alternate-day Fasting in Nonobese Subjects: Effects on Body Weight, Body Composition, and Energy Metabolism. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/15640462/

‌The good news is that most evidence suggests that ADF does not increase compensatory eating in the way that traditional caloric restriction weight loss diets do. Compensatory eating refers to overheating after caloric restriction.13Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011

Compensatory eating is deleterious to weight loss efforts because it can essentially undo the caloric deficit you have generated.14Keim, N. L., Stern, J. S., & Havel, P. J. (1998). Relation between circulating leptin concentrations and appetite during a prolonged, moderate energy deficit in women. The American Journal of Clinical Nutrition68(4), 794–801. https://doi.org/10.1093/ajcn/68.4.794

A person eating a bowl of cereal and fruit.

#4: ADF Diets May Preserve Muscle Mass

One of the downsides of dieting is that it can potentially reduce your muscle mass. Because muscle mass requires more calories to fuel per day, when you lose muscle mass, your metabolic rate drops. This can make it harder to maintain weight loss.

Some studies15Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936 have found that alternate day fasting may help preserve lean body mass more than daily caloric restriction, though some studies have not found this to be the case.

#5: Alternate Day Fasting May Improve Health

Lastly, while many people take on an alternate day fasting diet for weight loss, there are also health benefits of fasting every other day.

Alternate day fasting results may improve blood sugar management and reduce the symptoms and risk of type 2 diabetes by reductions in visceral fat mass, fasting insulin, and insulin resistance.16,Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013

It can also improve heart health and other risk factors for heart disease, such as improving cholesterol levels. (Decrease in total cholesterol, LDL cholesterol, and triglycerides.)17Varady, K. A., Bhutani, S., Church, E. C., & Klempel, M. C. (2009). Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. The American Journal of Clinical Nutrition90(5), 1138–1143. https://doi.org/10.3945/ajcn.2009.28380

Intermittent fasting can also support autophagy, the process of cellular cleanup.18Alirezaei, M., Kemball, C. C., Flynn, C. T., Wood, M. R., Whitton, J. L., & Kiosses, W. B. (2010). Short-term fasting induces profound neuronal autophagy. Autophagy6(6), 702–710. https://doi.org/10.4161/auto.6.6.12376

‌Not sure if alternate day fasting is right for you? Check out some of our other intermittent fasting diet guides here.

Intermittent fasting written on a notebook with a clock, plate and utensils.

References

  • 1
    Hoddy, K. K., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., & Varady, K. A. (2014). Meal timing during alternate day fasting: Impact on body weight and cardiovascular disease risk in obese adults. Obesity22(12), n/a-n/a. https://doi.org/10.1002/oby.20909
  • 2
    Klempel, M. C., Kroeger, C. M., & Varady, K. A. (2013). Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet. Metabolism62(1), 137–143. https://doi.org/10.1016/j.metabol.2012.07.002
  • 3
    S, B., Mc, K., Cm, K., Jf, T., & Ka, V. (2013, July 1). Alternate Day Fasting and Endurance Exercise Combine to Reduce Body Weight and Favorably Alter Plasma Lipids in Obese Humans. Obesity (Silver Spring, Md.). https://pubmed.ncbi.nlm.nih.gov/23408502/
  • 4
    Varady, K. A., Bhutani, S., Church, E. C., & Klempel, M. C. (2009). Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. The American Journal of Clinical Nutrition90(5), 1138–1143. https://doi.org/10.3945/ajcn.2009.28380
  • 5
    Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936
  • 6
    Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936
  • 7
    Das, S. K., Gilhooly, C. H., Golden, J. K., Pittas, A. G., Fuss, P. J., Cheatham, R. A., Tyler, S., Tsay, M., McCrory, M. A., Lichtenstein, A. H., Dallal, G. E., Dutta, C., Bhapkar, M. V., DeLany, J. P., Saltzman, E., & Roberts, S. B. (2007). Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial. The American Journal of Clinical Nutrition85(4), 1023–1030. https://doi.org/10.1093/ajcn/85.4.1023
  • 8
    Klempel, M. C., Bhutani, S., Fitzgibbon, M., Freels, S., & Varady, K. A. (2010). Dietary and physical activity adaptations to alternate day modified fasting: implications for optimal weight loss. Nutrition Journal9(1). https://doi.org/10.1186/1475-2891-9-35
  • 9
    Lk, H., Sr, S., Ck, M., Sd, A., & E, R. (2005, January 1). Alternate-day Fasting in Nonobese Subjects: Effects on Body Weight, Body Composition, and Energy Metabolism. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/15640462/
  • 10
    Varady, K. A., Hudak, C. S., & Hellerstein, M. K. (2009). Modified alternate-day fasting and cardioprotection: relation to adipose tissue dynamics and dietary fat intake. Metabolism58(6), 803–811. https://doi.org/10.1016/j.metabol.2009.01.018
  • 11
    Catenacci, V. A., Pan, Z., Ostendorf, D., Brannon, S., Gozansky, W. S., Mattson, M. P., Martin, B., MacLean, P. S., Melanson, E. L., & Troy Donahoo, W. (2016). A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity24(9), 1874–1883. https://doi.org/10.1002/oby.21581
  • 12
    Lk, H., Sr, S., Ck, M., Sd, A., & E, R. (2005, January 1). Alternate-day Fasting in Nonobese Subjects: Effects on Body Weight, Body Composition, and Energy Metabolism. The American Journal of Clinical Nutrition. https://pubmed.ncbi.nlm.nih.gov/15640462/
  • 13
    Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011
  • 14
    Keim, N. L., Stern, J. S., & Havel, P. J. (1998). Relation between circulating leptin concentrations and appetite during a prolonged, moderate energy deficit in women. The American Journal of Clinical Nutrition68(4), 794–801. https://doi.org/10.1093/ajcn/68.4.794
  • 15
    Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Internal Medicine177(7), 930. https://doi.org/10.1001/jamainternmed.2017.0936
  • 16
    ,Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013
  • 17
    Varady, K. A., Bhutani, S., Church, E. C., & Klempel, M. C. (2009). Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. The American Journal of Clinical Nutrition90(5), 1138–1143. https://doi.org/10.3945/ajcn.2009.28380
  • 18
    Alirezaei, M., Kemball, C. C., Flynn, C. T., Wood, M. R., Whitton, J. L., & Kiosses, W. B. (2010). Short-term fasting induces profound neuronal autophagy. Autophagy6(6), 702–710. https://doi.org/10.4161/auto.6.6.12376
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.