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Original Investigation
January 12, 2004

Effects of the Amount of Exercise on Body Weight, Body Composition, and Measures of Central Obesity: STRRIDE—A Randomized Controlled Study

Author Affiliations

From the Divisions of Cardiology (Drs Slentz, Duscha, and Kraus, Mss Johnson and Aiken, and Mr Ketchum), Geriatric Medicine (Dr Bales), and General Internal Medicine (Dr Samsa), Department of Medicine, Duke Center for Living (Dr Kraus), Center for Health Policy Research (Dr Samsa), and Department of Community and Family Medicine (Dr Samsa), Duke University Medical Center, Durham, NC; and Geriatric Research, Education and Clinical Center (Dr Bales), Durham Veterans Affairs Medical Center, Department of Exercise and Sports Science and Human Performance Laboratory, East Carolina University, Greenville, NC (Dr Houmard). The authors have no relevant financial interest in this article.

Arch Intern Med. 2004;164(1):31-39. doi:10.1001/archinte.164.1.31
Abstract

Background  Obesity is a major health problem due, in part, to physical inactivity. The amount of activity needed to prevent weight gain is unknown.

Objective  To determine the effects of different amounts and intensities of exercise training.

Design  Randomized controlled trial (February 1999–July 2002).

Setting and Participants  Sedentary, overweight men and women (aged 40-65 years) with mild to moderate dyslipidemia were recruited from Durham, NC, and surrounding communities.

Interventions  Eight-month exercise program with 3 groups: (1) high amount/vigorous intensity (calorically equivalent to approximately 20 miles [32.0 km] of jogging per week at 65%-80% peak oxygen consumption); (2) low amount/vigorous intensity (equivalent to approximately 12 miles [19.2 km] of jogging per week at 65%-80%), and (3) low amount/moderate intensity (equivalent to approximately 12 miles [19.2 km] of walking per week at 40%-55%). Subjects were counseled not to change their diet and were encouraged to maintain body weight.

Main Outcome Measures  Body weight, body composition (via skinfolds), and waist circumference.

Results  Of 302 subjects screened, 182 met criteria and were randomized and 120 completed the study. There was a significant (P<.05) dose-response relationship between amount of exercise and amount of weight loss and fat mass loss. The high-amount/vigorous-intensity group lost significantly more body mass (in mean [SD] kilograms) and fat mass (in mean [SD] kilograms) (−2.9 [2.8] and −4.8 [3.0], respectively) than the low-amount/moderate-intensity group (−0.9 [1.8] and −2.0 [2.6], respectively), the low-amount/vigorous-intensity group (−0.6 [2.0] and −2.5 [3.4], respectively), and the controls (+1.0 [2.1] and +0.4 [3.0], respectively). Both low-amount groups had significantly greater improvements than controls but were not different from each other. 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.

Conclusions  In nondieting, overweight subjects, the controls gained weight, both low-amount exercise groups lost weight and fat, and the high-amount group lost more of each in a dose-response manner. 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.

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