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What is Alternate Day Fasting? + Benefits, Schedule, Common Questions

What is Alternate Day Fasting? + Benefits, Schedule, Common Questions

  • September 03, 2020
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For original article click here

Alternate day fasting, also known as ADF or the every other day diet, has been sparking an interest in people worldwide. When I first started looking into alternate day fasting, I couldn’t find much about what it is on the internet and you may be in the same shoes as I was.

I’ve put together this science-backed, comprehensive post about what alternate day fasting is, it’s benefits, an example schedule, and some common questions you may have. This way you won’t need to play needle in the haystack for information.

I’ve also included a simple excel file for a typical month of alternate day fasting if it helps!

Contents hide

1 Alternate Day Fasting – What is it?1.1 The Two Methods of Alternate Day Fasting

1.1.1 True Alternate Day Fasting

1.1.2 Modified Alternate Day Fasting

1.2 Eating Days

1.3 Fasting Days

2 10 Benefits of Alternate Day Fasting Backed by Science

2.1 Benefit #1: Weight loss With Improved Body Composition

2.2 Benefit #2: Autophagy

2.3 Benefit #3: Increased Human Growth Hormones

2.4 Benefit #4: Decreased Risk of Cancer

2.5 Benefit #5: Improved Cardiovascular System

2.6 Benefit #6: Increased Endurance

2.7 Benefit #7: Increased life span

2.8 Benefit #8: May Boost Your Metabolism

2.9 Benefit #9: Better Cognitive Function

2.10 Benefit #10: May help with Anxiety and Depression

2.11 Bonus Benefit: Save Money

3 Answers to Common Alternate Day Fasting Questions

3.1 Is Alternate day fasting Safe?

3.2 Who Should Not Do Alternate Day Fasting?

3.3 What can I drink while doing Alternate Day Fasting?

3.4 What Occurs in the Body During the Fasting Period?

3.5 Will I lose my muscles while fasting?

3.6 Is fasting the same as starving?

4 What to Expect When Doing Alternate Day Fasting

4.1 Fatigue (At First)

4.2 Hunger

4.3 Social Pressure

5 Alternate Day Fasting Schedule

5.1 Example Schedule of Week 1

5.2 Example of Easing Into Alternate Day Fasting

6 Alternate Day Fasting – That’s It

7 Sources

Alternate Day Fasting – What is it?

Alternate day fasting is considered one of the more intensive types of intermittent fasting methods. It simply involves alternating between eating and fasting days rather than specific hours of a day.

This makes alternate day fasting the simplest method of intermittent fasting. You simply eat every other day.

The Two Methods of Alternate Day Fasting

True Alternate Day Fasting

True Alternate day fasting is the ‘true’ form of fasting on alternate days, meaning it is a true 0 calorie fast. This would entail being able to eat for one day and then completely abstain from food for the next day and repeat.

True ADF has been shown to provide many benefits due to the longer period of fasting and can have a significant reduction of body fat. It is highly recommended that on your eating day there should be no calorie restrictions but an effort to take in an excess of nutrient rich foods to avoid any form of deficiencies.

Modified Alternate Day Fasting 

Modified Alternate day fasting does not have a true fasting period. During your fasting period you can intake 15%-25% of your BMR or 500 calories. These calories should ideally be taken in with one meal that is comprised of fats and proteins since these satiate your body and are nutrient dense. Sugars and Carbs may leave you feeling hungrier and irritable, increasing the chance of failure to follow through. Weight loss will not be as accelerated in this version but can be more sustainable for some.

If you are doing Modified Alternate day fasting, a quick 500 calorie meal that I would recommend includes:

  • 3 eggs (~250 calories)
  • A serving of plain greek yogurt (~140 calories)
  • A side of fruit and vegetables or nuts (~110 calories)

– A side of fruit and vegetables or nuts (~110 calories)

Keep in mind, some of the benefits from fasting may be toned down due to this fast having a ‘break.’

You can check out a more detailed comparison here to know type of alternate day fasting is right for you.

Eating Days

Your eating days are to be normal eating days with no form of calorie restriction or counting. It is recommended to take in about 125% – 150% of your basal metabolic rate (BMR) in the form of healthy, nutrient dense foods to ensure there is no form of malnutrition. Eating well on your eating day can play a big factor when it comes to getting through your fasting day. Regardless of what is consumed, unless you’re eating your two days worth of calories in one, weight loss will be achieved.

Fasting Days

On your fasting days you are to completely abstain from all foods, taking in 0 calories throughout the entire day unless you choose to do the modified version.

Your fasted hours are going to normally be about 36 hours since you have your last meal at the night of your eating day, then one day (24 hours), plus how long you are asleep for on your eating day (about 8 hours.) For some tips to get through your fast, check out my 12 tips to get through your fast!

Now that we know a bit more about Alternate day fasting, let’s take a look at the amazing benefits.

10 Benefits of Alternate Day Fasting Backed by Science

In the same way that exercise, though a stress on the body, is good for you, periods of fasting cause stress on the body but are good for you in the same way. These sorts of stress on our body are called hormetic stress. With mild levels of ‘harmful’ factors our body begins “fostering the cellular capacity of maintenance and repair.”   

Benefit #1: Weight loss With Improved Body Composition

Unlike other forms of weight loss such as many diet fads or traditional calorie restriction diets, alternate day fasting changes the way your body metabolizes energy. The period of fasting puts our body into a state of ketosis in which we tap directly into our fat stores for energy. During this state, our protein oxidation, or how much protein we burn for energy, is decreased resulting in less muscle loss than a traditional calorie restriction diet.

Kevin D. Hall

A study done on Obesity reached an interesting conclusion when comparing the differences in weight loss between the methods of calorie restriction (CR) and alternate day fasting.

Weight loss was basically the same and showed no statistical difference, BUT percentage of fat mass lost was higher in the ADF  group and they also retained more lean mass than the CR group.

Benefit #2: Autophagy

Fasting starts a process called Autophagy which basically means “to eat oneself,” and it is the process in which our body begins to destroy old and damaged cells. This process is common in the body and is necessary to get rid of dysfunctional cells but is amplified during periods of fasting.

After about 24 hours of fasting, autophagy in the body is increased and as growth hormones also increase – you are literally ‘remodeling’ the cells in your body. This prevents the growth of tumors, replaces a chunk of your immune system with fresh new cells, and is linked to longevity in multiple studies.

Benefit #3: Increased Human Growth Hormones

Human Growth Hormones (HGH) are critical in many aspects of our health and are responsible for cell growth, cell healing, boosting metabolism, and burning fat.

In This study, HGH levels increase rapidly when fasting has begun and eventually reaches to about 2000% of baseline levels on the 5th day of fasting.

Ho, Veldhuis, Johnson, Furlanetto, Evans, Alberti, Thorner

This is primarily released to counteract any of our bodies efforts to burn lean mass while in a fasted state in order to preserve strength. Had our bodies not been able to prevent muscle loss while fasting, our ancestors would have struggled greatly.

Though with alternate day fasting you are not going 5 days in a row, you can expect increased HGH levels on your fasting days.

Benefit #4: Decreased Risk of Cancer

Cancer has been one of the top killers of the world’s population and has only been increasing overtime. Besides decreased risk of cancer from weight loss and reduction of visceral fat, alternate day fasting affects another factor associated with reduced risk of developing cancer: cell proliferation rate. This rate determines how quickly both healthy and cancerous cells multiply.

When testing how ADF affects this proliferation rate, the results came back with a 49% decrease in cell proliferation rates. This decrease slows down the possibility of a mutation occurring as well as slowing down or even halting cancer growth.

In another study two groups of rats were given tumor cells. The group that did alternate day fasting had a survival rate of 50% after 10 days while the non-ADF group only had a 12.5% survival rate.

Benefit #5: Improved Cardiovascular System

It was found in this study, mice that were subjected to alternate day fasting showed a lower resting heart rate and lower blood pressure than mice that were not on ADF.

The cardiovascular system may benefit from fasting the same way it does with endurance training and enhances stress resistance the same way as well.

In a human study, research shows intermittent fasting can decrease cardiovascular risk factors substantially. The studies show a 7 – 32% decrease in LDL cholesterol as well as significant reductions in blood pressure (3 – 8%.)

These changes primarily are driven by the substantial weight loss caused by intermittent fasting methods.

Benefit #6: Increased Endurance

More advanced intermittent fasting regimens have been shown to increase endurance. In a one month study of resistance training, a group of young men did a 20 hour fast – 4 days / week. During this period, they were given several upper and lower body exercises consisting of 4 sets and 8 – 12 repetitions.

It was found that this group performed better in terms of endurance compared to the control group who did not fast.

The intermittent fasting group also did not have any loss in lean muscle mass, just fat mass, although calorie intake was about 650 less than their suggested maintenance calories.

Benefit #7: Increased life span

Alternate day fasting has been shown to increase life span through the activation of a special gene called SIRT1. SIRT1 is a key regulator of many cellular processes and can alter insulin pathways as well as promote resistance to oxidative stress and reduce the death of cells.

Normally found to be the cause of increased life span in mice, It has been shows that SIRT1 is upregulated during alternate day fasting. This results in reduced oxidative stress, lower overall inflammation, and increased health and life.

Benefit #8: May Boost Your Metabolism

Scientists put mice into what they called an eating every other day fasting routine (alternate day fasting) and compared them with mice that were free to eat as much as they wanted, whenever.

Although both groups of mice ended up having the same cumulative food intake over the course of 30 days, the mice in the alternate day fasting routine lost a lot of weight while the rest gained some weight.

Below are graphs from the study showing the results of the two groups of mice: AL for Ad Libitum (no restriction on food intake) and EODF for every other day fasted mice.

In figure B, both groups ate the same amount, but the AL group shows a slight increase in body mass while the EODF group shows a large drop in body mass (looks to be about 15%.) The scientists also observed that this weight loss was specifically fat and lean mass was preserved.

Li G, Xie C, Lu S, Nichols RG, Tian Y, Li L, Patel D, Ma Y, Brocker CN, Yan T, Krausz KW, Xiang R, Gavrilova O, Patterson AD, Gonzalez FJ.

In figure E, we see an increased average energy expenditure contrary to popular belief that periods of not eating will bring your metabolism to a halt and decrease energy expenditure.

In figure D we can see that overall body temperature is increased which the study found to be due to the increased utilization of fat cells for energy.

So, with periods of fasting, our body is burning more fat for heat and thus increasing the speed of our metabolism.

Benefit #9: Better Cognitive Function

During fasting our ketones signal the activation of Brain-Derived Neurotrophic Factors (BDNF) which is also released during exercise. BDNF has a primary function of repairing and strengthening our brain cells and increasing neuronal plasticity (ability to adapt and learn)

Researchers put mice through a Barnes Maze test – a test of learning and memory that requires the mice to use visual cues to reach a specific target. The type of intermittent fasting the mice were doing was a 22:2, so they ate for only 2 hours a day and fasted for 22 hours.

They measured a few things on this test: Number of errors, whether they remembered the target, and the percentage of success relative to which group did better.

After 14 days of training and running the test, the intermittent fasting group had 38% less errors, were 20% more successful, and spent 15 seconds less on acting on the cues they received. By the 14th day, the intermittent fasting group was much better at remembering around where the target was than their counterparts.

Brandhorst, S., Choi, I. Y., Wei, M., Cheng, C. W., Sedrakyan, S., Navarrete, G., Dubeau, L., Yap, L. P., Park, R., Vinciguerra, M., Di Biase, S., Mirzaei, H., Mirisola, M. G., Childress, P., Ji, L., Groshen, S., Penna, F., Odetti, P., Perin, L., Conti, P.S., Longo, V. D.

Benefit #10: May help with Anxiety and Depression

A protein called IL-1B has both been linked to higher states of anxiety as well as higher trait anxiety and can even affect a person’s response to stress. So researchers set out to study if alternate day fasting in a healthy state could affect levels of IL-1B and anxiety.

After putting mice through periods of 24hr fasting and 24hr eating periods, they measured IL-1B gene expression across the entire brain and found that it was significantly reduced. This means that theoretically, the mice should exhibit less signs of anxious behavior.

These mice were put into an elevated zero maze which is just a long circular corridor-like table and measured the behaviors exhibited by the fed and fasted mice. The fasted mice spent 70% more time and moved a further distance compared to the fed mice.

This could be an increase in confidence in the mice to spend more time exploring the unknown instead of freezing with anxiety.

Remember the BDNF I spoke about earlier in terms of better brain function and memory?

BDNF levels also appear to be correlated with mood regulation and depression. Though a decline of BDNF levels doesn’t necessarily mean a depressed mood, an increase is linked to increased neuroplasticity.

An increase in neuroplasticity is related to healthier behavior in majorly depressed patients that were given anti-depressants.

It is hard to know whether fasting will have the exact same affect, but if neuroplasticity improves depression and allows for healthy cognition, then fasting methods may be a viable method to prevent and potentially cure depression.

Bonus Benefit: Save Money

The average weekly amount spend on food in America is about $54. This number obviously depends on several factors such as did this person go out to eat or not.

With alternate day fasting, you’re going to save half of what you normally spend on food since you will be eating only half the week. This is great news for your wallet (but not the food industry.)

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Answers to Common Alternate Day Fasting Questions

Is Alternate day fasting Safe?

There are two studies I dove into to answer this question since it may be the most important.

One study looked at 59 obese individuals to measure how safe alternate day fasting is and found that, “ADF produces minimal adverse outcomes, and has either benign or beneficial effects on eating disorder symptoms.”

These minimal adverse outcomes included things like constipation, some weakness, and bad breath. This is nothing compared to the plethora of benefits associated with implementing a fasting regimen that you will soon scroll upon.

The second study focused on long term effects of alternate day fasting in healthy individuals and found only benefits in the people who did ADF for more than 6 months and no negative effects.

Based on the research, chances are that ADF is safer than being overweight or obese.

Thinking about this logically. Our bodies have been built to undergo periods of fasting since food was not always in such abundance. Having any negative consequences to this would not benefit our survival and so our body has establish mechanisms to deal with fasting in a positive manner.

(You do always want to check with your physician first.)

Who Should Not Do Alternate Day Fasting?

Those who have previously struggled with eating disorders should not experiment with Alternate day fasting. Pregnant and Nursing women should also not do any type of fasting. If you have any health conditions be sure to check with your doctor prior to trying any form of intermittent fasting.

What can I drink while doing Alternate Day Fasting?

You should make sure to drink water throughout your fasting day as much as you feel a thirst for. Drinking too much water can cause an electrolyte balance and leave you feeling unwell.

I personally haven’t had the need to, but if you do, an electrolyte supplement with no additives is recommended. People usually recommend this one. You can also make your own ‘Snake Juice’:

  • 8 cups (2 liters) of water
  • 1/2 teaspoon (2 g) of Himalayan pink salt
  • 1 teaspoon (5 g) of salt-free potassium chloride
  • 1/2 teaspoon (2 g) of food-grade Epsom salts

Black coffee and unsweetened teas are going to be your best friend on your fasting days. Though there is some debate whether they break your fast, It most likely won’t (keeping sane is important.)

They are one of the few things you can drink that has some taste and the caffeine will also boost your energy and increase your metabolic rate by 11%. If you can’t tolerate caffeine, there is always decaf versions and herbal teas.

Drinks with artificial sweeteners are up to you but there is research that suggests some artificial sweeteners may cause an insulin spike just by the taste of sweetness alone.

For a list, check out 6 Things You Can Drink While Fasting.

What Occurs in the Body During the Fasting Period?

You may be wondering what happens in your body during a period of fasting this long, so here is a breakout for you.

After about 12 hours of fasting, our body begins to enter a state of ketosis. In this stage, our glucose reserves are being depleted and so our body begins to switch over to breaking down our fat cells for energy.

By the 18th hour of your fast, your body is in a deeper level of ketosis and is burning fat at a higher rate.

At the 24 hour mark of your fast, the process called autophagy is increasing throughout your body, recycling old and damaged cells and DNA.

Now as your fast comes to an end near the 36 hour mark, you’re going to be burning pure fat, and in an even deeper state of autophagy. At this point your going to really feel light and will be reaping the full benefits of fasting.

Once you finally break your fast with a nutritious and balanced meal, your body will utilize the food very efficiently because of your increased insulin sensitivity, clearing glucose out of the blood and feeding our cells.

Will I lose my muscles while fasting?

As with anything that can put you in a state of a calorie deficit, your muscle mass will decrease during alternate day fasting unless you can put yourself in a calorie surplus during your eating day but that can be difficult.

As I mentioned above, your human growth hormones (HGH) begin to rise during a period of fasting to counteract any muscle oxidation. This study shows that you lose less lean mass with fasting methods compared to calorie restriction methods, so you can be reassured that alternate day fasting is a better form of weight loss for your muscles.

Is fasting the same as starving? 

A huge misconception when doing any sort of fasting regimen, is that you are starving your body. Starving is very detrimental to overall health but is not the same as fasting.

Our bodies are biologically adapted for periods of fasting and therefore have capabilities to change the way energy is metabolized in our bodies.

When starving, your body has depleted all its fat stores or cannot access the fat stores. This leads to the breakdown of muscles, bones, and even organs for nutrition.  If you have excess levels of fat on your body, fasting will not cause you to starve.

What to Expect When Doing Alternate Day Fasting

Fatigue (At First)

Until you become fat-adapted (more efficient in using fat for energy) you may have less energy. This gets better with time as you adjust and can be sometimes helped with replenishing your electrolytes. Sometimes caffeine can help too.


To be concise, you’re going to be hungry!

The feeling of hunger is not true hunger. Our gut releases a hormone called Ghrelin that signals to our brain that it is time for food.

Ghrelin is primarily controlled by our normal eating periods, so if you eat at 12pm every day, you will most likely feel hungry at that time everyday. After years of multiple meals throughout the day, we must give our Ghrelin levels the time to adjust to the new eating pattern until the hunger pangs go away.

As you begin fasting, over time your Ghrelin response will become weaker and weaker. I personally began to feel the decrease in hunger on my fasting days after about 2 weeks of Alternate day fasting. Unfortunately until then, it will require some will.

Social Pressure

Food is very culturally intertwined with being social. You really begin to see this when you begin to implement fasting. It is best to let those around you know what your plans are and explain to them what you are doing. Hopefully, this article can help equip you to explain to others what you are doing as well as the benefits. In order to maintain a healthy social life, knowing the social C.U.E.S of fasting can help you out.

Alternate Day Fasting Schedule

Below are two simple schedules of alternate day fasting based on how much experience you have with fasting to give you an idea of what it will look like and how to do it.

If you have experience with intermittent fasting regimens, you can start by having your day 1 be your eating day and then begin your fasting day on day 2.

Example Schedule of Week 1

Day Fast / Eat
Sunday Eat
Monday Fast
Tuesday Eat
Wednesday Fast
Thursday Eat
Friday Fast
Saturday Eat

Note: The Sunday of week 2 would continue the trend by being a fasting day. You can choose to eat on weekends, but this would then be called a 4:3 intermittent fast.

If you are new to intermittent fasting, it is best to begin with a less intensive method on alternate days and increase your fasting window every week until you have a full day of fasting.

Example of Easing Into Alternate Day Fasting

Week 1 16:8 (Fast for 16 hours on alternate days only)
Week 2 20:4 (Fast for 20 hours on alternate days only)
Week 3 Modified alternate day fasting (500 calories on fasting day)
Week 4 Begin true alternate day fasting

Sure, this will take a few weeks, but ensures you are easing into it to adjust to the periods of fasting and not feel unwell. Keep in mind that fat loss will still occur with these other methods as well as the benefits of fasting.

Here’s a simple alternate day fasting schedule / calendar I put together:Download

Alternate Day Fasting – That’s It

Alternate day fasting is hands down, the simplest method of intermittent fasting that will result in amazing weight loss and tons of other benefits, as you just learned.

I hope this helped you in understanding ADF and equipped you to give it a try for yourself if your health permits.

If there are any points you believe I may have missed or questions you would like me to answer, leave a comment below!

Happy Fasting!


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