A new study published in the July 18 Annals of Internal Medicine says exercising without dieting is as effective for modest weight loss as dieting without exercising.

Researchers in Canada studied 52 men with abdominal obesity for 12 weeks. The men were divided into four different study groups: weight loss by dieting; exercise intended to produce weight loss; exercise designed not to produce weight loss; or no special diet or exercise (the control group).

Investigators measured the men's weight, total body fat, proportion of body fat in the abdomen, body muscle and physical fitness at the beginning and end of the study. In addition, the men were tested for early signs of diabetes.

"Currently, no compelling evidence supports the observation that exercise alone is not a useful method for reducing total or abdominal body fat," says Dr. Robert Ross of Queen's University in Kingston, Ontario. "Our findings are in stark contrast to previous observations. Although we reaffirm that diet restriction is effective for reducing total and abdominal obesity, our findings also demonstrate that 12 weeks of approximately 60 minutes of daily exercise without caloric restriction is associated with substantial reductions in body weight."

The researchers report men in both the diet and the exercise-weight loss programs lost about 16 pounds. The weight of the men in the other two groups did not change. Ross and colleagues note, however, that all men who exercised, even the ones who did not lose weight, experienced an increase in physical fitness.

The researchers point out that obesity is related to developing diabetes, as well as high blood pressure and heart disease.