Morbid obesity (defined as a body mass index (BMI) >40) is a severe and increasingly prevalent condition in developed countries. On top of medical dysfunctions a large proportion of these patients also suffer from psychosocial dysfunctions and psychiatric disorders. Prior to bariatric surgery a substantial percentage of patients suffer from binge eating disorder or binge eating symptoms. Surgery is carried out not only to reduce short term morbidity and mortality in patients with morbid obesity but it also gives a chance for a long-term weight loss. To achieve this goal many patients need some kind of psychiatric intervention. Objective:The principal aim of this study is to evaluate the impact of bariatric surgery on psychiatric disorders and psychological dysfunctions of patients with morbid obesity over the course of a year following surgery. Special consideration is given to the presence of psychiatric comorbidity, eating disorders, body image dissatisfaction and self-esteem.Design: Longitudinal, psychiatric intervention previous and one year after surgery. Results:The mean age of the patients was 41.7 years (SD=2.4) The mean weight was 121.8 kg (22.5) which corresponds to a mean BMI of 45.7 (7.7). The sex distribution is 20% male and 80% female patients. Psychiatric disorders (ICD-10 criteria), were present in 32.5 %. Among them eating disorders were the most prevalent (38.5%). Following bariatric surgery there was a significant improvement in eating disorders and eating symptoms (according to the Eating Disorders Inventory and the Bulimic Test of Edimburgh) and in body image satisfaction (measured by BSQ) and self steem (Rosemberg). A multiple regression analysis of clinical factors associated to weight loss showed that 40% of it is determined by the decrease of bulimic symptoms detected by the BITE-symptoms. Conclusion:Morbid obesity is a risk population for psychiatric disorders and psychological dysfunctions. Bariatric Surgery reduces over one year the severity of this morbidity. The impact of increased self-esteem through the increase of body image satisfaction and of the increase in control over food intake seems to be the major factor in these changes.