Alternate Day Intermittent Fasting Put to the Test

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

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
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, who has conducted 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 or dinner, or as small meals throughout the day .

Some people may find that alternate day fasting is easier to stick to than other types of diets.

However, a yearlong study found that adherence when following alternate day fasting (where calorie intake was reduced to 25% of energy needs on fasting days) was not superior to 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.