Obesity can be defined as an excess of adipose tissue. It is associated to a significantly increased risk of cardiovascular disease, hypertension, diabetes mellitus and hypercholesterolemia. The results of the Italian survey called Okkio alla Salute (2010), which was attended over 42'000 students of third-class of primary school and 44'000 parents, confirm bad eating habits, sedentary lifestyles and excess weight. In particular, 22,9% of the children resulted overweight and 11,1% obese. The prevalence of obesity is higher in the south of Italy than in the north and in males rather than in females. Moreover, parents do not always have a real idea of the physical aspect of their son: 36% of the mothers of overweight or obese children are do not believe their child is overweight. Just 29% of them think that the quantity of food eaten by their child is excessive. The relative risk for an obese child to become an obese adult increases with the age and is directly correlated to the severity of overweight. Among obese children of preschool age, 26 to 41% will be an obese adult., Among scholar children, the percentage increases to 69%. The paper describes a multidisciplinary approach the disease, in fact, dietary and behavioural modifications, associated with physical activity, have the purpose of educate overweight and of preventing the onset of complications or reducing their severity if already present and reversible.