Alternate-Day Fasting Shows Promise for Obese Dieters

Restricting daily calorie intake is a common plan to help obese and overweight people slim down to healthier weights. But the regime requires a daily 15 to 40 percent calorie reduction, which makes sticking to the diet hard for many.

University of Illinois at Chicago researchers have found that a modified version of a plan called "alternate-day fasting" may be easier to abide and has the added bonus of improving cardio health. The findings appear in the November 1 issue of The American Journal of Clinical Nutrition.

"This diet has been around about 20 years, but its effect on weight loss hadn't really been studied," said Krista Varady, assistant professor of kinesiology and nutrition, who led the UIC research team.

The 10-week trial studied 16 clinically obese people - 12 women and four men - between the ages of 35 and 65 who all weighed more than 210 pounds, had kept their weight stable for the previous three months, and had body mass indexes of between 30 and 39.9. None was diabetic, had a history of cardiovascular disease, was taking weight-loss or lipid- or glucose-lowering medications, or smoked.

The study was divided into three phases:

The first two weeks, participants ate and exercised normally.

Between weeks three and six, participants ate normal meals one day then would fast the next. On fast days, participants ate the equivalent of a three-course lunch prepared by UIC's Human Nutritional Research Center. The meal provided between 20 and 25 percent of daily energy needs.

For the final four weeks, participants were counseled by dietitians on menu options, but essentially chose on their own what to eat, based on what they had learned about meal sizes and food choices.

"We wanted to see if they could actually do it by themselves - because what's the point of studying this diet if you have to feed people meals prepared at metabolic kitchens all the time?" said Varady.

Weight loss ranged from 10 to 30 pounds; the researchers expected an average loss of only five pounds. Blood pressure and heart rate were also lowered, along with total cholesterol and circulating fat levels.

Varady hopes now to study the effects of staying on the diet for at least six months, looking for evidence of self-motivation and to see if the diet helps in maintaining proper weight.

"Why are some able to do it but others not? It takes about two weeks to adjust to the diet, after which people don't feel hungry on the fast day," she said.

"We need to find out how long they can stay on this diet - and if they go off it, do they automatically regain the weight?"

Co-authors on the study are doctoral students Surabhi Bhutani and Monica Klempel, and Emily Church, clinical coordinator in physical therapy at UIC. The study was supported by UIC departmental funding.