Adulthood and childhood obesity is rapidly becoming an epidemic problem and it has a short and long-term impact on health. Short-term consequences are mostly represented by psychological effects; in fact obese children have more chances to develop psychological or psychiatric problems than non-obese children. The main long-term effect is represented by the fact that childhood obesity continues into adulthood obesity and this results in negative effects in young adult life, since obesity increases the risk to develop morbidity and premature mortality. The obesity-related diseases are mostly represented by hypertension, type 2 diabetes, dyslipidemia, cardiovascular diseases. Medical treatment should be discouraged in childhood because of the side effects and it should be only reserved for obese children with related medical complications. Lifestyle changes should be encouraged in both adulthood and childhood obesity. This review focuses on the management of obesity both in adulthood and in childhood, paying particular attention to lifestyle changes that should be recommended.