A summary of the epidemiology, etiology and therapy of obesity is given with special emphasis on psychosomatic aspects. Overweight and obesity are widespread and go hand in hand with an increased health risk. The etiology of obesity is multifactorial based on gene/environment interactions; hyperalimentation and physical inactivity, as an expression of the rapid technical advancements within the past decades, have, however, had a decisive influence on the pandemic spreading of obesity. The prevalence of mental disorders is increased particularly in obese women. Although phylogenetically of relevance, an environment that associates slimness with beauty, health, physical and mental proficiency leads to a stigmatization of the obese. The results are mental symptoms and disorders. On the contrary, mental problems up to and including the full clinical picture of mental disorders may lead to changes in eating and exercise behaviour, the result of which may be a sustained positive energy balance with overweight and obesity. The success of conservative weight reduction measures in obesity is inadequate. Surgical measures are more successful, but they are only indicated for severe obesity. The psychosomatic and psychotherapeutic approach to overweight and obesity is multifactorial and indispensable. Obesity is not an eating disorder; it may, however, be the result of hyperalimentation into which pathogenetic and mental factors have been incorporated.