Obesity is a serious chronic disease, associated with severe sequelae and increased mortality rates, and therefore requires long-term care. This article gives an overview of the current state of research on psychotherapeutic treatment of obesity, focusing on behavioral approaches. Systematic well-controlled studies on humanistic and psychodynamic therapies are not available. A small number of studies on psychotherapy-related approaches, e.g. relaxation therapy or hypnotherapy, failed to demonstrate any decisive positive outcomes. While weight loss programs using methods of behavior therapy and lifestyle modification approaches result, on the average, in a short-term weight loss of 10% of the initial weight, long-term effects of such programs are disappointing. Further evidence suggests, however, that long-term maintenance programs may facilitate lasting behavioral changes of patients in their daily lives and work against weight regain. More research on effective maintenance programs is called for to further improve care of obese patients; it should lay stronger emphasis on internet-based weight maintenance programs.