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.
Copyright by the American Society for Clinical Nutrition.

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