Alternate-Day Fasting


Calorie restriction is of course known to aid in weight loss, but many obese patients just can’t follow that path. Alternate-day fasting, or ADF, makes it easier for them to comply, because it doesn’t have to be all the time.

A study of alternate-day fasting and coronary artery disease showed that “modified ADF is an effective, short term dietary intervention to help obese individuals lose weight and total body fat mass.” In this study, only six weeks of ADF improved some of the key biomarkers, like fat mass, blood pressure, and waist circumference.

Alternate-day fasting is what it sounds like — on the fasting days, the person drinks no-calorie beverages, period. Modified ADF allows 500 calories on the “fasting” days. Still, it seems to help not only to lower heart disease risk but to avoid type 2 diabetes. ADF seems to have better effects on leptin and ghrelin, the satiety and hunger hormones, than constant calorie restriction. The blood tests for cholesterol and triglycerides come back looking a lot better than before.

Experienced alternate day fasters say it takes about two weeks to really get into the swing of things. ADF is also said to be easier to stick with when supervision has decreased. The indications are that ADF is better at preserving muscle mass — which is good — while constant calorie restriction may be detrimental to that purpose.

An ADF-er can lose as much as 8 percent of original body weight in 12 weeks or possibly sooner. It works especially well for the middle-aged, particularly when combined with exercise. It is said to be easier to comply with than full-time calorie restriction, because on the non-fasting days the person eats whatever, and it does not even seem to matter if their diet is low-fat or high-fat.

ADF gurus

The “Every Other Day” diet was created by Krista Varady, Ph.D., and Bill Gottlieb, CHC, who characterize it as revolutionary, science-proven, and easy-to-follow. Here’s what they say:

You’ll find only one rule: eat no more than 500 calories on Diet Day, eat anything you want and as much as you want on Feast Day, and alternate those two days. That’s it! No counting calories, carbs, fat or protein. No avoiding any particular food; all foods are allowed. There are no complex meal preparations and plans.

In their initial studies, participants were told to make have big meal in the middle of the day. But that made it difficult to either share family dinnertime or go out for a dinner as a social occasion. About one-third of the subjects complained about lunch being the fast-day meal. Now, the team says the fast-day meal can be at any point during the predetermined (usually 8-hour) window.

Not ADF fans

Researchers recruited 100 obese people, who were randomly assigned to A) fast on alternate days, B) follow a traditional diet, or C) continue to do whatever they usually did. The study lasted for a year, which is unusually long compared to previous studies of the same method. Angela Chen reported for

The people in the alternate-day fasting group were told to eat about 25 percent of their normal daily calories on their fast days and 125 percent on their “feast” days. The people in the normal dieting group just cut about 25 percent of their calories every day. Nobody was allowed to join a gym. At the end of the year, both groups had lost about 6 percent of their body weight, and there weren’t a lot of differences when it came to things like cholesterol, insulin resistance, and blood pressure.

Every study has its dropouts. In this case, there were more dropouts from the fasting group than from either of the other two. Dr. Varady described herself as “shocked” to learn that it was harder for people to stick with alternate-day fasting than with daily calorie restriction.

Your responses and feedback are welcome!

Source: “The effects of modified alternate-day fasting diet on weight loss and CAD risk factors in overweight and obese women,” JDMDOnline, 2013
Source: “Alternate-Day Fasting — A Comprehensive Beginner’s Guide,”, 10/12/16
Source: “The Every Other Day Diet,”, undated
Source: “Superfast diet,”, undated
Source: “Fasting every other day isn’t as good of a weight loss method as you think,”, 05/01/17
Photo credit: Quinn Dombrowski (quinn.anya) on Visualhunt/CC BY-SA

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
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Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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