Alternate-Day Fasting – A Comprehensive Beginner’s Guide

Alternate-day fasting is one way to do intermittent fasting.

On this diet, you fast every other day, but eat whatever you want on the non-fasting days.

The most common version of this diet actually involves “modified” fasting where you can eat 500 calories on fasting day.

Alternate-day fasting is a very powerful weight loss tool, and can help lower your risk of heart disease and type 2 diabetes.

Here is a detailed beginner’s guide to alternate-day fasting.

How to Do Alternate-Day Fasting

Alternate-day fasting (ADF) is an intermittent fasting approach.

The basic idea is that you fast on one day, and then eat what you want the next day.

This way you only need to restrict what you eat half of the time.

On fasting days, you’re allowed to drink as many calorie-free beverages as you like. Examples include water, unsweetened coffee and tea.

If you’re following a modified ADF approach, you’re also allowed to eat about 500 calories on fasting days, or 20–25% of your energy requirements.

The most popular version of this diet is called “The Every Other Day Diet” by Dr. Krista Varady. She also did most of the studies on ADF.

The health and weight loss benefits seem to be the same regardless of whether the fasting-day calories are consumed at lunch, dinner or as small meals throughout the day.

Studies show that many people find alternate-day fasting much easier to stick to than traditional, everyday calorie restriction.

Most of the studies on alternate-day fasting used the modified version, with 500 calories on fasting days. This is considered much more sustainable than doing full fasts on fasting days, but it’s just as effective.

In this article, the terms “alternate-day fasting” or “ADF” generally apply to the modified approach with about 500 calories on fasting days.

Bottom Line: Alternate-day fasting cycles between days of fasting and normal eating. The most popular version allows for about 500 calories on fasting days.

Alternate-Day Fasting and Weight Loss

ADF is very effective for weight loss.

Studies among overweight and obese adults show it may make you lose 3-8% of your body weight in 2–12 weeks.

Interestingly, ADF seems to be particularly effective for weight loss among middle-aged people.

Studies have shown that ADF and daily calorie restriction are equally effective at reducing harmful belly fat and inflammatory markers in obese individuals.

However, a 2016 review study concluded that ADF may be superior to daily calorie restriction diets, given that it’s easier to stick to, produces greater fat loss and preserve more muscle mass.

Furthermore, combining ADF with endurance exercise may cause twice as much weight loss than ADF alone and six times as much weight loss as endurance exercise alone.

In regards to diet composition, ADF seems to be equally effective whether it’s done with a high-fat or low-fat diet.

Bottom Line: Alternate-day fasting is very effective for weight loss and may be easier to stick to than traditional calorie restriction.

Alternate-Day Fasting and Hunger

The effects of ADF on hunger are rather inconsistent.

Some studies show that hunger ultimately goes down on fasting days, while others state that hunger remains unchanged.

However, research agrees that modified ADF with 500 calories on fasting days is much more tolerable than full fasts on fasting days.

One study comparing ADF to calorie restriction showed that ADF caused slightly more favorable changes in the satiety hormone leptin and the hunger hormone ghrelin.

Similarly, animal studies have shown that modified ADF resulted in decreased amounts of hunger hormones and increased amounts of satiety hormones than other diets.

Another factor to consider is compensatory hunger, which is a frequent downside of traditional, daily calorie restriction.

Compensatory hunger refers to increased levels of hunger in response to calorie restriction, which cause people to eat more than they need to when they finally “allow” themselves to eat.

Studies have shown that ADF does not increase compensatory hunger as much as continuous calorie restriction.

In fact, many people who try modified ADF claim that their hunger diminishes after the first two weeks or so. After a while, some find that the fasting days are nearly effortless.

However, the effects of ADF on hunger most likely vary by individual.

Bottom Line: The effects of alternate-day fasting on hunger are inconsistent. Studies on modified alternate-day fasting show that hunger decreases as you adapt to the diet.

Alternate-Day Fasting and Body Composition

ADF has been shown to have unique effects on body composition, both while you are dieting and during your weight-maintenance period.

Studies comparing traditional calorie-restricted diets and ADF show that they are equally as effective at decreasing weight and fat mass.

However, ADF seems to be more effective at preserving muscle mass.

This is really important, as losing muscle mass along with fat decreases the amount of calories your body burns on a daily basis.

One randomized controlled study compared ADF to a traditional, calorie-restricted diet with a 400-calorie deficit.

Both after an eight-week study and 24 unsupervised weeks, no difference was observed in weight regain between the groups.

However, after the 24 unsupervised weeks, the ADF group had preserved more muscle mass and lost more fat mass than the calorie-restricted group.

Bottom Line: Alternate-day fasting is more effective at preserving muscle mass during weight loss than other weight loss methods.

Health Benefits of Alternate-Day Fasting

ADF has several health benefits aside from weight loss.

Type 2 Diabetes

Type 2 diabetes accounts for 90–95% of diabetes cases in the US.

What’s more, more than a third of Americans have pre-diabetes, a condition in which blood sugar levels are higher than normal but not high enough to be considered diabetes.

Losing weight and restricting calories is usually an effective way to improve or reverse many symptoms of type 2 diabetes.

Similarly to continuous calorie restriction, ADF seems to cause mild reductions in risk factors for type 2 diabetes among overweight and obese individuals.

However, ADF seems most effective at lowering insulin levels and reducing insulin resistance, while only having a minor effect on blood sugar control.

Having high insulin levels (hyperinsulinemia) has been linked to obesity and chronic diseases, such as heart disease and cancer.

Among pre-diabetic individuals, 8–12 weeks of ADF have been shown to decrease fasting insulin by about 20–31%.

A reduction in insulin levels and insulin resistance should lead to a significantly reduced risk of type 2 diabetes, especially when combined with weight loss.

Bottom Line: Alternate-day fasting may reduce risk factors for type 2 diabetes. It can reduce fasting insulin levels by 20-31% in pre-diabetic individuals.

Heart Health

Heart disease is the leading cause of death in the world, responsible for about 1 in 4 deaths.

Many studies have shown that ADF is a good option for overweight and obese individuals to lose weight and reduce heart disease risk factors.

Most studies on the subject range from 8–12 weeks and are done in overweight and obese individuals.

The most common health benefits include:

• Reduced waist circumference (2–2.8 in or 5–7 cm).
• Decreased blood pressure.Lower LDL cholesterol concentration (20–25%).
• Increased number of large LDL-particles and reduction in the dangerous small, dense LDL particles.
• Decreased blood triglycerides (up to 30%).

Bottom Line: Alternate-day fasting may reduce waist circumference, decrease blood pressure, lower LDL cholesterol and decrease blood triglycerides.

Alternate-Day Fasting and Autophagy

One of the most common effects of fasting on the body is the stimulation of autophagy.

Autophagy is a process in which old parts of cells are degraded and recycled. It plays a key role in preventing diseases such as cancer, neurodegeneration, heart disease and infections.

Animal studies have consistently shown that both long-term and short-term fasting increase autophagy and are linked to a delay in aging and reduced risk of tumors.

Furthermore, fasting has been shown to increase lifespan in rodents, flies, yeasts and worms.

Moreover, cell studies have shown that fasting stimulates autophagy, resulting in effects that may help keep your body healthy and help you live longer.

This has been confirmed by human studies showing that ADF diets reduce oxidative damage and promote changes that may be linked to longevity.

The findings look very promising, but the effects of ADF on autophagy and longevity need to be studied more extensively.

Bottom Line: Alternate-day fasting stimulates autophagy in animal and cell studies. This process may slow down aging and help prevent diseases such as cancer and heart disease.

Does Alternate-Day Fasting Induce Starvation Mode?

Nearly all weight loss methods cause a slight drop in resting metabolic rate.

This effect is often called “starvation mode,” but the technical term is adaptive thermogenesis.

When you severely restrict your calories, your body starts conserving energy by reducing the amount of calories it burns. It can make you stop losing weight and feel miserable.

However, ADF does not seem to cause this drop in metabolic rate.

One study compared the effects of standard calorie restriction and ADF for eight weeks.

The results showed that continuous calorie restriction significantly decreased resting metabolic rate by 6%, while ADF only caused an insignificant 1% reduction.

What’s more, after 24 unsupervised weeks, the calorie restriction group still had a 4.5% lower resting metabolic rate than at the beginning of the study. Meanwhile, the ADF participants maintained their original metabolic rate.

Several effects of ADF may be responsible for counteracting this drop in metabolic rate, including the preservation of muscle mass.

Bottom Line: Alternate-day fasting does not seem to decrease metabolic rate in the same way as continuous calorie restriction. This may be because ADF helps to preserve muscle mass.

Is It Also Good for Normal-Weight People?

ADF is good for more than just weight loss — it can also have health benefits for normal-weight people.

A 3-week study analyzed normal-weight individuals following a strict ADF diet, with zero calories on fasting days.

The researchers found that it resulted in increased fat burning, decreased fasting insulin and a 4% decrease in fat mass.

However, hunger levels remained quite high throughout the study, and they speculated whether a modified ADF diet with one small meal on fasting days might be more tolerable for normal-weight people.

Another controlled study in both normal-weight and overweight individuals showed that following an ADF diet for 12 weeks reduced fat mass and produced favorable changes in risk factors for heart disease.

That being said, ADF generally provides you with much fewer calories than you need to maintain weight, which is the reason why people ultimately lose weight.

If you’re not looking to lose weight or fat mass or are underweight to begin with, other dietary methods will probably suit you better.

Bottom Line: Alternate-day fasting increases fat burning and reduces risk factors for heart disease in normal-weight people.

What to Eat and Drink on Fasting Days

There is no general rule on what you should eat or drink on fasting days, except that your total calorie intake should not exceed 500 calories.

It’s best to drink low-calorie or calorie-free drinks on fasting days, such as water, coffee and tea.

Most people find it best to eat one “big” meal late in the day, while others prefer to eat early or split the amount between 2–3 meals.

Since your calorie intake will be severely limited, it’s best to focus on nutritious, high-protein foods, as well as low-calorie vegetables. These will make you feel full without many calories.

Soups may also be a good option on fasting days, as they tend to make you feel fuller than if you ate the ingredients on their own.

Here are a few examples of meals that are suitable for fasting days:

•        Eggs and vegetables.
•        Yogurt with berries.
•        Grilled fish or lean meat with vegetables.
•        Soup and a piece of fruit.
•        A generous salad with lean meat.

You can find numerous recipes for quick 500-calorie meals and healthy low-calorie snacks on Google and Pinterest.

Bottom Line: There are no strict guidelines regarding what to eat and drink on fasting days. It’s best to stick to high-protein foods and vegetables, as well as low-calorie or calorie-free beverages.

Is Alternate-Day Fasting Safe?

Studies have shown that alternate-day fasting is safe for most people.

It does not result in a greater risk of weight regain than traditional, calorie-restricted diets. On the contrary, it may even be better for long-term weight loss than continuous calorie restriction.

Some think that ADF increases your risk of binge eating, but studies found that it actually decreased depression and binge eating. It also improved restrictive eating and body image perception among people with obesity.

That being said, there are always groups of people who should not adhere to any weight loss diet.

These include people with eating disorders, pregnant and lactating mothers, children and those who are underweight or have certain medical conditions.

You should check with a doctor before trying this if you have a medical condition or are currently taking any medications.

Bottom Line: Alternate-day fasting has an outstanding safety profile. It does not increase binge eating or raise your risk of weight regain after you stop the diet.

Take Home Message

Alternate-day fasting is a very effective way to lose weight.

It has several benefits over traditional calorie-restricted diets, and is linked to major improvements in many health markers.

The best part of all is that it is surprisingly easy to stick to, because you only need to “diet” every other day.

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Intermittent Fasting Explained - Will It Help You Lose Weight?

Now this does sound easy! 

11 Myths About Fasting and Meal Frequency

Intermittent fasting has become immensely popular in recent years.

This is an eating pattern that cycles between periods of fasting and eating.

However, there are still all sorts of myths surrounding this topic.

This article debunks the 11 most common myths about fasting, snacking and meal frequency.

1. Skipping Breakfast Will Make You Fat

“Breakfast is the most important meal of the day.”

There is an ongoing myth that there is something “special” about breakfast.

People believe that breakfast skipping leads to excessive hunger, cravings and weight gain.

Although many observational studies have found statistical links between breakfast skipping and overweight/obesity, this may be explained by the fact that the stereotypical breakfast skipper is less health-conscious overall.

Interestingly, this matter was recently settled in a randomized controlled trial, which is the gold standard of science.

This study was published in 2014 and compared eating breakfast vs skipping breakfast in 283 overweight and obese adults.

After a 16-week study period, there was no difference in weight between groups.

This study shows that it doesn’t make any difference for weight loss whether you eat or don’t eat breakfast, although there may be some individual variability.

However, there are some studies showing that children and teenagers who eat breakfast tend to perform better at school.

There are also studies on people who have succeeded with losing weight in the long term, showing that they tend to eat breakfast.

This is one of those things that varies between individuals. Breakfast is beneficial for some people, but not others. It is not essential and there is nothing “magical” about it.

Bottom Line: Eating breakfast can have benefits for many people, but it is not essential. Controlled trials do not show any difference between eating and skipping breakfast for the purpose of weight loss.

2. Eating Frequently Boosts Your Metabolism

“Eat many, small meals to stoke the metabolic flame.”

 Many people believe that eating more meals leads to increased metabolic rate, so that your body burns more calories overall.

It is true that the body expends a certain amount of energy digesting and assimilating the nutrients in a meal.

This is termed the thermic effect of food (TEF), and amounts to about 20-30% of calories for protein, 5-10% for carbs and 0-3% for fat calories.

On average, the thermic effect of food is somewhere around 10% of the total calorie intake.

However, what matters here is the total amount of calories consumed, not how many meals you eat.

Eating six 500-calorie meals has the exact same effect as eating three 1000-calorie meals. Given an average thermic effect of 10%, it is 300 calories in both cases.

This is supported by numerous feeding studies in humans, showing that increasing or decreasing meal frequency has no effect on total calories burned.

Bottom Line: There is no difference in calories burned if you eat more frequently. Total calorie intake and macronutrient breakdown is what counts.

3. Eating Frequently Helps Reduce Hunger

Some people believe that snacking helps prevent cravings and excessive hunger.

Interestingly, several studies have looked at this, and the evidence is mixed.

Although some studies suggest that more frequent meals lead to reduced hunger, other studies find no effects, and yet others show increased hunger levels.

One study that compared 3 high-protein meals to 6 high-protein meals found that 3 meals were actually better for reducing hunger.

That being said, this may depend on the individual. If snacking helps you experience fewer cravings and makes you less likely to binge, then it is probably a good idea.

However, there is no evidence that snacking or eating more often reduces hunger for everyone. Different strokes for different folks.

Bottom Line: There is no consistent evidence that eating more often reduces overall hunger or calorie intake. Some studies even show that smaller, more frequent meals increase hunger.

4. Many, Smaller Meals Can Help You Lose Weight

Frequent meals do not boost metabolism (increase calories out).

They also do not seem to reduce hunger (reduce calories in).

If eating more frequently has no effect on the energy balance equation, then it shouldn’t have any effect on weight loss.

In fact, this is supported by science. Most studies on this do show that meal frequency has no effect on weight loss.

For example, a study in 16 obese men and women did not find any difference in weight, fat loss or appetite when comparing 3 and 6 meals per day.

However, if you find that eating more often makes it easier for you to eat fewer calories and less junk food, then perhaps this is effective for you.

Personally I find it to be ridiculously inconvenient to eat so often, making it even harder to stick to a healthy diet. But it may work for some people.

Bottom Line: There is no evidence that changing your meal frequency helps you lose more weight. Most studies show that there is no difference.

5. The Brain Needs a Constant Supply of Glucose

Some people believe that if we don’t eat carbs every few hours, that our brains will stop functioning.

This is based on the belief that the brain can only use glucose (blood sugar) for fuel.

However, what is often left out of the discussion is that the body can easily produce the glucose it needs via a process called gluconeogenesis.

This may not even be needed in most cases, because your body has stored glycogen (glucose) in the liver that it can use to supply the brain with energy for many hours.

Even during long-term fasting, starvation or a very low-carbohydrate diet, the body can produce ketone bodies from dietary fats.

Ketone bodies can provide energy for part of the brain, reducing its glucose requirement significantly.

So, during a long fast, the brain can easily sustain itself using ketone bodies and glucose produced from proteins and fats.

It also makes no sense from an evolutionary perspective that we shouldn’t be able to survive without a constant source of carbohydrate. If that were true, then humans would have become extinct a long time ago.

However, some people do report that they feel hypoglycemic when they don’t eat for a while. If this applies to you, then perhaps you should stick to a higher meal frequency, or at least ask your doctor before changing things.

Bottom Line: The body can produce glucose to supply the brain with energy, even during long-term fasts or starvation. Part of the brain can also use ketone bodies for energy.

6. Eating Often and Snacking is Good For Health

It is simply not “natural” for the body to be constantly in the fed state.

When humans were evolving, we had to endure periods of scarcity from time to time.

There is evidence that short-term fasting induces a cellular repair process called autophagy, where the cells use old and dysfunctional proteins for energy.

Autophagy may help protect against aging and diseases like Alzheimer’s disease, and may even reduce the risk of cancer.

The truth is that fasting from time to time has all sorts of benefits for metabolic health.

There are also some studies suggesting that snacking, and eating very often, can have negative effects on health and raise your risk of disease.

For example, one study found that, coupled with a high calorie intake, a diet with more frequent meals caused a greater increase in liver fat, indicating that snacking may raise the risk of fatty liver disease.

There are also some observational studies showing that people who eat more often have a much higher risk of colorectal cancer.

Bottom Line: It is a myth that snacking is inherently good for health. Some studies show that snacking is harmful and others show that fasting from time to time has major health benefits.

7. Fasting Puts Your Body in “Starvation Mode”

One common argument against intermittent fasting is that it can put your body in “starvation mode.”

According to the claims, not eating makes your body think it is starving, so it shuts down its metabolism and prevents you from burning fat.

It is actually true that long-term weight loss can reduce the amount of calories you burn. This is the true “starvation mode” (the technical term is adaptive thermogenesis).

This is a real effect, and can amount to hundreds of fewer calories burned per day.

However, this happens with weight loss no matter what method you use. There is no evidence that this happens more with intermittent fasting than other weight loss strategies.

In fact, the evidence actually shows that short-term fasts increase metabolic rate.

This is due to a drastic increase in blood levels of norepinephrine (noradrenaline), which tells the fat cells to break down body fat and stimulates metabolism.

Studies show that fasting for up to 48 hours can actually boost metabolism by 3.6-14%. However, if you fast much longer than that, the effect can reverse and metabolism can go down compared to baseline.

One study showed that fasting every other day for 22 days did not lead to a decrease in metabolic rate, but the participants lost 4% of their fat mass, which is impressive for a period as short as 3 weeks.

Bottom Line: It is false that short-term fasting puts the body in “starvation mode.” The truth is that metabolism actually increases during fasts of up to 48 hours.

8. The Body Can Only Use a Certain Amount of Protein Per Meal

There are some who claim that we can only digest 30 grams of protein per meal, and that we should eat every 2-3 hours to maximize muscle gain.

However, this is not supported by science.

Studies do not show a difference in muscle mass if you eat your protein in more frequent doses.

The most important factor for most people is the total amount of protein consumed, not how many meals it is spread over.

Bottom Line: The body can easily make use of more than 30 grams of protein per meal, and it is not necessary to get protein in your body every 2-3 hours.

9. Intermittent Fasting Makes You Lose Muscle

Some believe that if we fast, that our bodies will start burning muscle and using it for fuel.

It is true that this happens with dieting in general, but there is no evidence that this happens more with intermittent fasting than other methods.

In fact, some studies even suggest that intermittent fasting is better for maintaining muscle mass.

In one review study, intermittent calorie restriction caused a similar amount of weight loss as continuous calorie restriction, but much less reduction in muscle mass.

There was also a study that had participants eat the same amount of calories as they were used to, except in one huge meal in the evening.

These people lost body fat and actually had a modest increase (almost statistically significant) in their muscle mass, along with a bunch of other beneficial effects on health markers.

Intermittent fasting is also popular among many bodybuilders, who find it to be an effective way to maintain high amounts of muscle with a low body fat percentage.

Bottom Line: There is no evidence that fasting causes more muscle loss than conventional calorie restriction. In fact, some studies show that intermittent fasting may be beneficial for holding on to muscle mass while dieting.

10. Intermittent Fasting is Bad For Your Health

Some people think that fasting can be downright harmful, but nothing could be farther from the truth.

Numerous studies show that intermittent fasting, and intermittent calorie restriction, can have incredibly impressive health benefits.

For example, intermittent fasting changes the expression of genes related to longevity and protection against disease, and has been shown to prolong lifespan in test animals.

It also has major benefits for metabolic health, such as improved insulin sensitivity, reduced oxidative stress and inflammation, and a reduction in various risk factors for heart disease.

It may also be good for brain health by boosting levels of a brain hormone called brain-derived neurotrophic factor (BDNF). This may be protective against depression and various other brain problems.

Bottom Line: Some think that fasting is harmful, but this is the opposite of the truth. Short-term fasting actually has powerful benefits for your body and brain.

11. Intermittent Fasting Makes You Overeat

Some claim that intermittent fasting won’t cause weight loss, because it causes you to overeat during the eating periods.

This is partly true. After a fast, people automatically tend to eat a little bit more than if they hadn’t been fasting.

In other words, they compensate for the calories “lost” during the fast by eating more during the next few meals.

However, this compensation isn’t complete. One study showed that people who fasted for a whole day only ended up eating about 500 extra calories the next day.

So they expended about 2400 calories during the fasting day, then “overate” by 500 calories the day after. The total reduction in calorie intake was then 1900 calories, which is a very large deficit for only 2 days.

Intermittent fasting reduces overall food intake while boosting metabolism. It also reduces insulin levels, increases norepinephrine and boosts human growth hormone as much as 5-fold.

Because of these factors, intermittent fasting makes you lose fat, not gain it.

According to a 2014 review study, fasting for 3-24 weeks causes body weight loss of 3-8%, and a 4-7% decrease in belly fat.

In this study, intermittent fasting caused 0.55 pounds of weight loss per week, but alternate-day fasting caused weight loss of 1.65 pounds per week.

The truth is, intermittent fasting is one of the world’s most powerful tools to lose weight.

Saying that it makes you overeat, go into “starvation mode” and end up gaining weight is the exact opposite of the truth.

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