The effect of exercise training on beta-adrenergic stimulation of fat metabolism in obese men

OBJECTIVE: To investigate the in vivo effect of exercise training at high a nd low intensity on beta -adrenergic stimulated fat metabolism in obese men at rest. METHOD: Twenty-three obese, healthy subjects were randomly divided in a low -intensity exercise training program (40% VO2max, n = 7), a high-intensity exercise training program (70% VO2max; n = 8), or a non-exercising control group (n = 8). The exercise training program lasted for 12 weeks with a tra ining frequency of 3 times per week. Before and after the intervention body composition and maximal aerobic capacity were measured as well as fat meta bolism at rest and during beta -adrenergic stimulation by isoprenaline. For comparison, six lean subjects served as a control group. They participated in a low-intensity exercise training program and underwent the same measur ements as the obese subjects. RESULTS: Relative fat oxidation decreased significantly during infusion of an increasing dose of isoprenaline in the obese low-intensity and high-inte nsity exercise training groups as well as in the lean group (P < 0.01). Exe rcise training failed to influence the effect of <beta>-adrenergic stimulat ion on relative fat oxidation in obese men at both intensities and in lean men. In addition, beta -adrenergic-mediated lipolysis did not seem to be di fferent after low intensity exercise training in lean and obese men. Lipoly sis might be increased after high-intensity exercise training in obese men. CONCLUSION: Low- and high-intensity exercise training in obese men failed t o affect beta -adrenergic mediated relative fat oxidation in vivo. beta -Ad renergic-mediated lipolysis might be increased in obese men after HI exerci se training only. The effect of low-intensity exercise training on beta -ad renergic-mediated fat metabolism was similar in lean and obese men.