Type 2 diabetes mellitus is becoming the most common type of diabetes in school children.

Obesity, now an epidemic in the USA, northern Europe, and Italy, is associated with several co-morbidities that shorten life expectancy, in particular type 2 diabetes mellitus (T2DM), arterial hypertension, and hyperlipidemia. The impact of obesity on mortality is evident in all ages, and is especially strong in young persons. Obesity, especially visceral obesity, associated with a sedentary lifestyle, is among the strongest risk factors for T2DM, and a diagnosis of T2DM seems to increase linearly as a function of duration of obesity. The pathogenesis of T2DM is based on a dual defect, i.e. increased insulin resistance coupled with defective insulin release. The main abnormality in obesity is increased insulin resistance, while insulin release, even though defective compared with body needs, is usually abundant. The incidence of obesity among children aged 6-16 years is now even greater than that among adults: in Italy, figures up to 30% have been reported. As in adults, obesity is a cause, among children, of arterial hypertension, left ventricular hypertrophy, hyperlipidemia, non-alcoholic-steato hepatitis, sleep apnea syndrome (SAS), and orthopedic, psychological, and social problems. Together with an increase in body weight, there is an increase of visceral fat. Obesity in children has also led to a tremendous increase in the prevalence of impaired glucose tolerance (IGT); the percentages span from 25% in a multiethnic cohort in the USA, to 4% in Italian Caucasians. Management of obesity and of T2DM in children has to face the issue of poor compliance; there is consensus that dietary treatment of obese T2DM children is a failure, so that drugs are required; the only drug evaluated in a formal trial is metformin, that behaves in terms of efficacy and of minor side effects as in adults. In conclusion, obesity in children is not pure obesity, but is accompanied by co-morbidities that cluster to form the "metabolic syndrome" just like in the adults. If this epidemics continues and is not properly challenged, in the next decades we will face an epidemic of early cardiovascular morbidity and mortality.