The aim of this study was to investigate the effect of aerobic exercise training on the lipolytic response of adipose tissue in obese subjects. Thirteen men (body mass index = 36.9 +/- 1.3 kg/m2) were submitted to aerobic physical training on a cycloergometer (30-45 min, 4 days a wk) for 3 mo. Adipocyte sensitivity to the action of catecholamines and insulin was studied in vitro before and after training. Training induced a decrease in the percentage of fat mass (P < 0.05) without changing the body weight. Basal lipolysis and hormone-sensitive lipase activity were significantly decreased after training (P < 0.05). The lipolytic effects of epinephrine, isoprenaline (beta-adrenoceptor agonist), and dobutamine (beta1-adrenoceptor agonist) were significantly increased (P < 0.05) but not those of procaterol (beta2-adrenoceptor agonist). The antilipolytic effects of alpha2-adrenoceptor and insulin were significantly decreased (P < 0.05). Lipolysis stimulation by agents acting at the postreceptor level was unchanged after training. In conclusion, aerobic physical training in obese male subjects modifies adipose tissue lipolysis through an enhancement of beta-adrenergic response and a concomitant blunting of adipocyte antilipolytic activity.