Effects of low- and high-intensity exercise training on body composition and substrate metabolism in obese adolescents

The objective was to investigate the effects of a 3-week weight-management program including moderate energy restriction and exercise training at 2 intensities [low intensity (LI): 40% and high intensity (HI): 70% maximal oxygen uptake (V′;_O2max)] on body composition, energy expenditure, and fat oxidation rate in severely obese adolescents. Twenty obese adolescents, aged 15-17 yr (body mass index: 37.5 kg/m²; 38.2% fat mass) participated in this study. Before starting (week 0, W0) and at the end of the weight-management period (week 3, W3), body composition was assessed by a multifrequency tetrapolar impedancemeter; basal metabolic rate (BMR), energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery by indirect calorimetry. At W3, body mass and fat mass decreased significantly (p2max, expressed in relative values, changed significantly only in the HI group by +0.010±0.006 l/(kg fat-free mass x min) (p=0.010). By contrast, no significant changes were observed at W3 in BMR, energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery. In conclusion, LI (40% of V′O₂max) physical activity favors fat oxidation and it seems advisable to encourage obese adolescents to perform LI physical activity which is more feasible and acceptable than intense exercise.