Overweight and obesity may develop in individuals with genetically determined low resting energy expenditure. Drugs are among the recognised precipitating factors. The obesity promoting impact of beta-blockers is, however, less well known. Resting energy expenditure, and thermogenesis induced by stimuli such as meals, cold and heat exposure, stress and anxiety, have a facultative component mediated by the sympathoadrenal system through catecholamines working on beta-adrenoceptors. Treatment with beta-blockers reduces the facultative thermogenesis by 50-100 kcal/d, which corresponds to the weight gain of 2-5 kg/year reported in clinical trials. Treatment with beta-blockers also results in insulin resistance, which may aggravate existing diabetes and elicit diabetes in predisposed patients. Overweight and obesity are frequently complicated with hypertension and angina pectoris, which are often treated with beta-blockers. Obesity is associated with a defective sympathetic activity, and treatment with beta-blockers may further reduce facultative thermogenesis and promote weight gain. The consequence may be aggravation of hypertension, insulin resistance and other atherogenic factors. The causal therapy of android overweight and obesity complicated with diabetes or hypertension is a sufficient weight loss. If pharmacological treatment is inevitable, combined treatment with diuretics and ACE-inhibitors are most appropriate.