BACKGROUND: Little is known about how the intensity of exercise influences cardiovascular fitness and body composition, especially in obese adolescents. OBJECTIVE: Our goal was to determine the effects of physical training intensity on the cardiovascular fitness, percentage of body fat (%BF), and visceral adipose tissue (VAT) of obese adolescents. DESIGN: Obese 13- to 16-y-olds (n = 80) were assigned to (1) biweekly lifestyle education (LSE), (2) LSE plus moderate-intensity physical training, or (3) LSE plus high-intensity physical training. The intervention lasted 8 mo. Physical training was offered 5 d/wk, and the target energy expenditure for all subjects in physical training groups was 1047 kJ (250 kcal)/session. Cardiovascular fitness was measured with a multistage treadmill test, %BF with dual-energy x-ray absorptiometry, and VAT with magnetic resonance imaging. RESULTS: The increase in cardiovascular fitness in the high-intensity physical training group, but not in the moderate-intensity group, was significantly greater than that in the LSE alone group (p = 0.009); no other comparisons of the 3 groups were significant. Compared with the LSE alone group, a group composed of subjects in both physical training groups combined who attended training sessions >= 2 d/wk showed favorable changes in cardiovascular fitness (p < 0.001), %BF (p = 0.001), and VAT (p = 0.029). We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition. CONCLUSIONS: The cardiovascular fitness of obese adolescents was significantly improved by physical training, especially high-intensity physical training. The physical training also reduced both visceral and total-body adiposity, but there was no clear effect of the intensity of physical training.
Copyright by the American Society for Clinical Nutrition.

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