Obesity is one of the most frequent diseases all over the world. It is associated to many complications in all organs and systems of the body and makes difficult the management of these disorders. Genetic and environmental factors interplay in its pathophysiology. Along an intrinsic predisposition, cultural and lifestyle patterns, characterized by excess energy intake and limited physical activity, lead to weight excess. Epidemiological studies have analyzed the associations of macro and micronutrients to the development of obesity. There are also numerous studies about different dietetic approaches, combined with physical activity and behavioral changes. Drug therapy may be indicated when BMI is above 30 kg/m2 and bariatric surgery may be considered for BMI higher than 35 kg/m2, if there are associated comorbidities than can improve with weight loss and there has been failure to lose weight with conventional measures. Long term follow up is mandatory after bariatric surgery to contribute to the prevention of weight regain.