EFFECTS OF STRENGTH OR AEROBIC TRAINING ON BODY-COMPOSITION, RESTING METABOLIC-RATE, AND PEAK OXYGEN-CONSUMPTION IN OBESE DIETING SUBJECTS

Given that resting metabolic rate (RMR) is related largely to the amou nt of fat-free mass (FFM), the hypothesis was that strength training, which stimulates muscle hypertrophy, would help preserve both FFM and RMR during dieting. In a randomized controlled intervention trial, mod erately obese subjects (aged 19-48 y) were assigned to one of three gr oups: diet plus strength training, diet plus aerobic training, or diet only. Sixty-five subjects (25 men and 40 women) completed the study. They received a formula diet with an energy content of 70% of RMR or 5 150 +/- 1070 kJ/d ((x) over bar +/- SD) during the 8-wk intervention. They were seen weekly for individual nutritional counseling. Subjects in the two exercise groups, designed to be isoenergetic, trained three times per week under supervision. Those in the strength-training grou p performed progressive weight-resistance exercises for the upper and lower body. Those in the aerobic group performed alternate leg and arm cycling. After 8 wk, the mean amount of weight lost, 9.0 kg, did not differ significantly among groups. The strength-training group, howeve r, lost significantly less FFM (P < 0.05) than the aerobic and diet-on ly groups. The strength-training group also showed significant increas es (P < 0.05) in anthropometrically measured flexed arm muscle mass an d grip strength. Mean RMR declined significantly, without differing am ong groups. Peak oxygen consumption increased the most for the aerobic group (P = 0.03). In conclusion, strength training significantly redu ced the loss of FFM during dieting but did not prevent the decline in RMR.