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 oxidatio n during the postdiet period. Reduced fat oxidation may contribute to weigh t regain. Objective: The present study investigated the effect of the addition of low -intensity exercise training to energy restriction on postdiet fat oxidatio n and on the contribution of the sympathetic nervous system to fat oxidatio n. Design: Forty obese men were divided randomly into 2 groups: diet (D) and d iet plus exercise (DE). Both groups followed an energy restriction program for 10 wk. Subjects in the DE group also participated in a low-intensity ex ercise training program [40% maximal oxygen uptake ((V) over dotO(2)max)] f or 12 wk. Before the intervention and after 12 wk, with subjects at stable body weights, we measured body composition, (V) over dotO(2)max, and substr ate oxidation at rest, during exercise at 50% (V) over dotO(2)max, and duri ng recovery. Measurements were made with and without administration of the beta -adrenergic antagonist propranolol. Results: Both interventions led to significant decreases in body weight, fa t mass, and fat-free mass (P < 0.001); these decreases did not differ signi ficantly between the D and DE groups. Neither intervention significantly af fected (V) over dotO(2)max. The effect of the intervention on the respirato ry exchange ratio differed significantly between the D and DE groups [two-w ay analysis of variance (ANOVA), P < 0.05]. The effect on the beta -adrener gic-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 restricti on counteracts the decline in fat oxidation during the postdiet period.