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College of Food, Agricultural, and Environmental Sciences


Chow Line: Alternate-day fast not a proven diet (for 11/29/09)

November 20, 2009

A friend is trying to lose weight by eating very little every other day. I don't think it's healthy, but she says it works. Is this kind of diet recommended?

Only a few studies have been done on what's called "alternate day fasting" (when you completely fast every other day) or a modified version (when you consume just 20 to 25 percent of your daily calorie needs every other day). Although the studies seem promising, they have been small and quite limited in scope. So, while this sort of technique may work for some people, we know far too little for it to get an official stamp of approval.

The latest study, appearing in the Nov. 1 issue of the American Journal of Clinical Nutrition, is a case in point. Researchers at the University of Illinois screened 52 people to take part, but only 20 met the researchers' criteria, including a stable weight for the past three months and no cholesterol- or glucose-lowering drugs. All were classified as obese, weighing at least 211 pounds.

The first two weeks of the study served as a control period -- participants were told to eat and exercise normally. During the next four weeks, every other day participants were given a 450-calorie lunch; this was the only food they were to eat on those days. On alternate days, they could eat what they wanted, but were to choose lean meats and dairy options to keep fat intake under control. During the study's last four weeks, participants prepared their own "fast day" meals in consultation with a dietitian. Researchers included this phase to see if people could keep up the regimen without having meals prepared for them.

Four people ended up dropping out of the study -- two because of the time commitment, and two because they couldn't adhere to the fast every other day. But the 16 who did complete the study (four men and 12 women) lost an average of 12 pounds. Plus, their total cholesterol, LDL cholesterol, triglyceride level, blood pressure and heart rate all decreased significantly. Researchers suggested that such a day-on, day-off schedule might be easier for some people to stick with than traditional diets. But even they admitted that 10 percent of the participants couldn't stay with the regimen for even eight weeks.

As with many weight-loss plans, it's hard to say what this means for any individual, especially over the long term. And from the current evidence, it's impossible to say how this type of diet affects nutrition: Could you get nutrients you need -- including fiber, calcium, iron and other minerals and vitamins -- if you fast every other day?

It's wise to be skeptical of such approaches. Still, it could work for some people, especially with proper nutrition counseling and, as with any balanced weight loss plan, a good dose of physical activity thrown in.

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or

Editor: This column was reviewed by Gail Kaye, nutrition specialist with Ohio State University Extension and lecturer in the Department of Human Nutrition, College of Education and Human Ecology.

Martha Filipic
Gail Kaye