Preoperative Dry Lean Body Mass as a Prognostic Factor for Excess Weight Loss After Bariatric Surgery.

Inclusion Criteria: * BMI ≥ 40 or BMI ≥ 35 kg/m2 and a complication that can be improved after bariatric surgery: cardiovascular disease including hypertension, severe metabolic disorder including type 2 diabetes, sleep apnea syndrome or other severe respiratory disorder, hepatic steatosis, disabling osteoarticular disease. * Patient requiring bariatric surgery (sleeve-gastrectomy or gastric bypass) * Patient who has agreed to participate in the study * Patient with social security coverage. Exclusion Criteria: * Patient with a contraindication to bariatric surgery (cognitive or psychological disorders, severe eating disorders, addiction to alcohol or psychoactive substances, contraindication to general anaesthesia, multiple history of digestive surgery, high risk of undernutrition (progressive cancer, chronic inflammatory bowel disease, cirrhosis, severe renal insufficiency...) * Pregnant or lactating women * Minor patient * Major patient under tutorship, curatorship, or deprived of liberty * Patient unable to understand protocol and / or give express consent * Patient not affiliated with a social security system or beneficiary of such a scheme * Patient participating in an intervention-type clinical research protocol likely to modify the evaluations of this protocol * adults under the protection of justice