[The Lausanne Obesity Cohort: why and how?].

Bariatric surgery has become the treatment of choice for severe obesity. The significant weight loss induced by these procedures is accompanied by spectacular improvements in the metabolic comorbidities that participate in morbidity and mortality of obesity. However, several questions remain open regarding the identification of patients that will benefit the most from the intervention or the long-term outcomes in terms of weight and co-morbidities.