Short-term effects of weight loss with or without low-intensity exercise training on fat metabolism in obese men.

BACKGROUND Energy restriction is known to induce a decline in fat oxidation during the postdiet period. Reduced fat oxidation may contribute to weight regain. OBJECTIVE The present study investigated the effect of the addition of low-intensity exercise training to energy restriction on postdiet fat oxidation and on the contribution of the sympathetic nervous system to fat oxidation. DESIGN Forty obese men were divided randomly into 2 groups: diet (D) and diet plus exercise (DE). Both groups followed an energy restriction program for 10 wk. Subjects in the DE group also participated in a low-intensity exercise training program [40% maximal oxygen uptake (VO2max)] for 12 wk. Before the intervention and after 12 wk, with subjects at stable body weights, we measured body composition, VO2max, and substrate oxidation at rest, during exercise at 50% VO2max, and during recovery. Measurements were made with and without administration of the beta-adrenergic antagonist propranolol. RESULTS Both interventions led to significant decreases in body weight, fat mass, and fat-free mass (P < 0.001); these decreases did not differ significantly between the D and DE groups. Neither intervention significantly affected VO2max. The effect of the intervention on the respiratory exchange ratio differed significantly between the D and DE groups [two-way analysis of variance (ANOVA), P < 0.05]. The effect on the beta-adrenergic-mediated respiratory exchange ratio tended to be different between the 2 groups (two-way ANOVA, P = 0.09). CONCLUSION Addition of low-intensity exercise training to energy restriction counteracts the decline in fat oxidation during the postdiet period.