Obesity is a global epidemic with serious health consequences. Behavior therapy is one of the evidence based methods in the treatment of obesity. According to several studies these programs induce modest (cca. 10%) weight reduction that is associated with statistically and clinically substantial improvements in weight-related health conditions and psychosocial outcomes. Reduced weight is usually maintained for a relatively long time, cca. 2-3 years. Cognitive and affective processes seem to play an important role in weight regain. This led to the development of cognitive behavioral treatment approaches. This paper describes the behavior therapy and cognitive-behavioral treatment of obesity.