Welcome to MyFitnessHub.com

Alternate-day Fasting:
A Healthy Alternative?

Robert Rice
June 17, 2009

An apple a day keeps the doctor away. But will an apple every other day keep fat away? MyFitnessHub.com finds out.


Alternate-Day Fasting, or ADF, is the latest fad in dieting, and many people claim that it has helped them lose weight. This involves eating as much as you want one day and eating less or nothing the next. For instance, bingeing on Day 1; consuming only sugar-free gum, tea, coffee or lots of water on Day 2; and then bingeing again on Day 3.

Of mice and men
Krista A. Varady of University of California, Berkeley and her colleagues conducted a study on the effects of alternate-day fasting on 24 male mice for four weeks. One group of mice was put under a complete ADF diet. Another group was allowed to consume only 50 percent of their regular diet every other day. The last group was allowed to consume 75 percent.

Her team found that the mice that followed the complete ADF diet (ADF-100%) lost weight and that the fat cells of both the ADF-100 and ADF-50% groups shrunk by more than half and by 35 percent, respectively. Also, in these two groups of mice, fat under the skin – but not abdominal fat – was broken down more than in mice that did not follow the diet.

Varady’s research team concluded that while complete and modified ADF regimens resulted in weight loss enough to lessen occurrences of obesity and type-2 diabetes, none of the ADF regimens lead to favorable fat or weight loss. More studies will be needed to confirm whether the long-term effects of ADF regimens are beneficial for health and disease reduction risk in humans.

Fasting: key to quick weight loss?
For thousands of years, fasting has been practiced for religious purposes. Now, people have come to use it as a way to lose weight. Aside from ADF, other types of fasting involve drinking nothing but water and juice; eating only raw vegetables and fruit; abstaining from meats; or performing a complete fast with no food and water. Advocates of periodic fasting acknowledge real weight-loss, but concede that it only happens if you eat moderately and healthfully on the days that you are not fasting, as well as avoid high fat, refined and processed food.

When you subject your body to a fast, it is forced to use energy stores, usually in the form of fat, to maintain normal body functions. However, when you eat less or no food, your metabolism slows down considerably to conserve your energy. When you break your fast and go back to your previous eating habits, your lowered metabolism may cause you to store more energy, thus cancelling out any weight loss you may have achieved. So while you may be able to starve some weight off, keeping those pounds from returning could prove that much harder.

Mark Mattson of the National Institute on Aging says, "Overeating is a big problem now in this country. It's particularly troublesome that a lot of children are overweight. The best way to somehow get people to eat less is still unclear." His team is currently planning a study to test the effect of regular fasting on people.

Of course, it is best to consult your doctor or a licensed dietitian before embarking on any type of fast, or any diet program for that matter.

Although people have been fasting for years for various reasons, for those seeking weight-loss, it is rarely permanent. Like most diet fads that have come and gone, ADF may soon pass. With growing scientific research, it probably will, and fast.