Spontaneous and stimulated lipolytic activity of subcutaneous abdominal adipocytes from obese subjects treated by a hypocaloric diet (800-1000 kcal/d) for 13-15 d were studied. A strong increase in basal lipolytic activity of the adipocytes occurred after the restrictive diet treatment. Linked to this phenomenon, an important alpha-adrenergic antilipolytic effect of adrenaline appeared whereas, the beta-stimulating effect of isoproterenol (beta-adrenomimetic drug) was not affected. The increased alpha-inhibitory effect of adrenaline was shown to theophylline-stimulated adipocytes of energy-restricted subjects. It is concluded that after a period of hypocaloric diet, the adrenaline-dependent lipolysis of subcutaneous abdominal fat cells of obese subjects is reversed. The lipolytic response induced by adrenaline, described in the adipocytes of obese controls, develop towards an alpha-adrenergic antilipolytic response after the hypocaloric treatment. Our data suggest that, in states with increased rate of lipolysis, there is an increased readiness for alpha-adrenergic response.