On-off fasting helps obese adults shed pounds

Fasting every other day can help obese people lose weight, a small study hints.

Even though the study participants ate whatever they wanted on their non-fasting days, they lost an average of 5.6 kilograms (about 12 pounds) after eight weeks, Dr. Krista A. Varady of the University of Illinois at Chicago and her colleagues found.

What's more, their total and "bad" LDL cholesterol levels dropped, and their blood pressure fell.

"People lost anywhere from about 7 pounds to about 30 pounds and that was in a very short amount of time," Varady said. And, she added, the program was pretty easy for the study participants to follow.

People typically try to lose weight by cutting their calorie intake every day, Varady and her team note in the American Journal of Clinical Nutrition. A much rarer approach, they add, is to have people alternate "feed days" with "fast days." Studies in normal and overweight people have shown that this strategy can indeed help people lose weight and improve their cholesterol levels.

To test alternate-day fasting in obese adults, Varady and her colleagues had 12 obese women and 4 obese men begin by eating normally for a two-week control period. Then, for eight weeks, they ate just 25 percent of the calories they needed to maintain their weight, between noon and 2 p.m., every other day.

For the first four weeks, the researchers provided study participants with their fasting day meal, while for the next four, study participants met with a dietitian every week and prepared the meal themselves.

Study participants lost about 0.7 kilograms (1.5 pounds) every week. At the end of the eight-week diet, their total cholesterol had dropped by 21 percent, on average, while their LDL cholesterol had dropped 25 percent. Moreover, their systolic blood pressure (the upper number in a blood pressure reading) had fallen by an average of five points.

While Varady and her team had thought people might overeat on their non-fasting day in order to compensate, this turned out not to be true; people typically ate between 100 percent or 125 percent of their calorie needs on their all-you-can eat days.

"I think it's probably because their stomachs kind of shrunk," she said.

The next step, the researcher said, will be to figure out if people can maintain the on-off approach for a longer period of time, to continue to lose weight or to maintain a healthy weight.

Anyone who wants to give the diet a try, she added, should meet with their doctor or a dietitian first.

SOURCE: American Journal of Clinical Nutrition, November 2009.