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Moderate amounts of exercise, such as walking 12 miles per week, may help prevent weight gain and can promote weight loss in non-dieting individuals, researchers say.
Results from the National Health and Nutrition Examination Survey 1999 indicate that an estimated 61 percent of U.S. adults are either overweight or obese, defined as having a body mass index (BMI) of 25 or more, according to the Centers for Disease Control and Prevention.
Obesity is associated with a higher risk for several health problems, including heart disease and diabetes. 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, according to Cris A. Slentz, Ph.D., of the Duke University Medical Center, Durham, N.C., and colleagues.
The researchers investigated the effects of different amounts and intensities of exercise on weight. The results are published in the Jan. 12, 2004, issue of Archives of Internal Medicine.
The randomized, controlled trial included 182 sedentary overweight men and women, ages 40-65 years, who were assigned to one of several groups: high amount/vigorous intensity exercise (equivalent to jogging about 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 in the study, 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 and hip circumference were measured. 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 their 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 wrote.