Fifty-five percent of Americans are overweight or obese, according to the article. From 1991 to 1998, the prevalence of obesity increased by almost 50 percent. Obesity is associated with a higher risk for several health problems, including heart disease and diabetes mellitus. It is widely believed that diet, combined with physical activity plays an important role in weight management, but the amount of activity needed to prevent weight gain is unknown.
Cris A. Slentz, Ph.D., from Duke University Medical Center, Durham, N.C., and colleagues investigated the effects of different amounts and intensities of exercise on weight.
The researchers conducted a randomized, controlled trial in which 182 sedentary overweight men and women (aged 40-65 years) were assigned to either: high amount/vigorous intensity exercise (equivalent to jogging approximately 20 miles per week at 65 percent to 80 percent peak oxygen consumption); low amount/vigorous intensity exercise (equivalent to 12 miles of jogging per week at 65 percent to 80 percent peak oxygen consumption); or low amount/moderate intensity exercise (equivalent to 12 miles of walking per week at 40 percent to 55 percent peak oxygen consumption). A fourth group (the control group) did not exercise. The study lasted eight months and participants were asked not to change their diets during this time. Body weight and waist circumference were measured. Of the 182 participants enrolled, 120 completed the study.
The researchers found that there was a clear relationship between the amount of physical activity and amount of weight loss, with the most weight loss seen in the high amount/vigorous intensity group, and the least in the low amount/moderate intensity group. The control group gained weight over the study period. Compared with the control group, all exercise groups significantly decreased abdominal waist and hip circumference measurements.
"These findings strongly suggest that, absent changes in diet, a higher amount of activity is necessary for weight maintenance and that the positive caloric imbalance observed in the overweight controls is small and can be reversed by a modest amount of exercise. Most individuals can accomplish this by walking 30 minutes every day," the authors write.
(Arch Intern Med. 2004;164:31-39. Available post-embargo at archinternmed.com) Editor's Note: This study was supported by a grant from the National Institutes of Health, Bethesda, Md.
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