ST. LOUIS — Which works best in fighting the risk factors for diabetes — exercise or diet? It's a toss up, according to a year-long study by Edward Weiss, a Saint Louis University researcher and a member of a Washington University team of scientists examining whether a calorie-restrictive diet can extend people's lifespan.

“Both diet and exercise provide profound benefits to reduce the risk of diabetes. Both those who restrict calories and those who exercise benefit from weight loss,” Weiss says. “We thought exercise probably would produce greater benefits. But both of these are providing beneficial health improvements.”

The researchers studied 50- to 60-year-olds whose body mass index was between 23 and 30. The study participants were divided into three groups with 18 each in the diet and exercise groups and 10 in the control group.

All participants had their insulin action and glucose tolerance evaluated at the beginning and end of the study. In addition, their weight, body composition and energy intake were measured at the beginning of the study and at one-, three-, six-, nine- and 12-month intervals. Those who restricted calories met weekly with a dietitian who helped them develop individualized menu plans. Exercisers had the goal of burning 16 percent more calories for the first three months, increasing to 20 percent the next nine months.

The study was published in the American Journal of Clinical Nutrition and funded by the National Institutes of Health.