Inclusion Criteria:  Non-menopausal women BMI between 35 and 45 kg/m² included HbA1c < 6.5% Social insured Ability to give consent  Exclusion Criteria:  moderate and severe kidney insufficiency hepatic insufficiency known gallbladder lithiasis history of cholecystectomy or cholecystectomy planned during the gastric bypass history of bariatric surgery except gastric band and gastric balloon history of NASH history of type 1 or 2 diabetes mellitus treatment interfering with the cortisol metabolism: taking oral or inhaled glucocorticoids within the last 6 months treatment by BA as ursodeoxycholic acid, bile acids sequester, statin, fibrate stopped less than 4 weeks ago