Effects of the Amount of Exercise on Body Weight, Body Composition, and Measures of Central Obesity

There was a significant dose-response relationship between amount of exercise and amount of weight loss and fat mass loss...

Compared with controls, all exercise groups significantly decreased abdominal, minimal waist, and hip circumference measurements. There were no significant changes in dietary intake for any group...

These finding strongly suggest that, absent changes in diet, a higher amount of activity is necessary for weight maintenance and that the positive caloric imbalance observed on the overweight controls is small and can be reversed by a modest amount of exercise.

--Slentz et al, Arch Intern Med, 2004