Obesity is an epidemic disease associated with numerous cardiovascular risk factors as diabetes mellitus, dyslipidemia, hypertension. Insulin resistance seems to be an important promoter for the development of most of these abnormalities. Besides genetic background, obesity, especially abdominal adiposity, is by far the most important factor for the development of type 2 diabetes. The treatment of a diabetic obese subject begins with diet and regular physical activity, eventually with a psychological support. In case of failure of such lifestyle approach alone, addition of drug therapy should be considered. It may include pharmacological agents able to promote weight loss (orlistat, sibutramine, possibly rimonabant) and/or antihyperglycaemic compounds capable of reducing insulin resistance (metformin, glitazones, acarbose). In case of severe/morbid obesity complicated with type 2 diabetes not well controlled with medical means, bariatric surgery is the only treatment that can induce an important and sustained weight loss, associated with marked improvement of metabolic control and amelioration of overall prognosis.