Alternate day fasting (ADF) involves fasting every other day, and it offers some of the same 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 article, we will explain what alternate day fasting is, alternate day fasting benefits, and how to do an ADF fasting diet.
We will cover the following:
- What Is Alternate Day Fasting?
- How to Do Alternate Day Fasting
- Benefits of Alternate Day Fasting
Let’s dive in!
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.
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, 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.This pattern would be continued throughout the week, alternating fasting 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.
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.
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 that 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 here is that this version makes ADF fasting more sustainable and approachable for people who cannot fathom water fasting every other day, either 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.
How to Do Alternate Day Fasting
As described, the official alternate day fasting diet involves water fasting every other day and then following a normal diet on the off 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.
This means that 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 seems to suggest that it doesn’t really matter when or how you split up your 500 calories on your caloric restriction fasting days.
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.
In other words, it seems that people lose the same amount of body fat 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.
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 or just improved health.
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 diets, 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.
Furthermore, if you are actually fasting 24 hours every other day, there may be some additional benefit of alternate day fasting intermittent 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 are following, you may not be fasting long enough to trigger some of the benefits of extended fasting.
For example, with a 14/10 intermittent fasting diet or a 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.
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 a lack of energy intake 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.
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 requirements every other day do not result in better long-term adherence than moderate, daily caloric restriction diets like traditional weight loss diets.
#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.
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.
Moreover, studies 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 research studies 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.
Other studies have found that hunger levels remain unchanged.
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.
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.
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.
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.
Compensatory eating is deleterious to weight loss efforts because it can essentially undo the caloric deficit you have generated.
#4: ADF Diets May Preserve Muscle Mass
One of the downsides of dieting is that it has the potential to 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 studies 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, improve heart health, improve other risk factors for heart disease such as cholesterol and abdominal obesity, and support autophagy, the process of cellular cleanup.
Not sure if alternate day fasting is right for you? Check out some of our other intermittent fasting diet guides here.
