Obesity during childhood and adolescence is an increasingly frequent cause for medical consultation. The increase in the prevalence of this disease, which has been considered as an epidemic by the World Health Organisation, is worrying. Obesity is a complex disease, whose aetiology still remains to be clarified due to the numerous factors involved: environmental, genetic, life style and behavioural, neuroendocrinological and metabolic. The persistence of childhood obesity until adulthood significantly increases the risk of suffering from diabetes mellitus, cardiovascular disease, hypertension, cholecystitis and cholelithiasis. Treatment of obesity is complicated and few patients regularly attend follow up examinations. A multidisciplinary team is required to carry out a suitable treatment, composed of paediatricians, dieticians, nurses, psychologists and psychiatrists. Successful treatment of obesity resides in reducing the calorie intake in relation to energy expenditure, and at the time providing instruction in appropriate eating habits and life styles that in the long term will promote the maintenance of the ideal weight.