Impact of a Pro-diversity Gut Microbiota Diet After a Bariatric Surgery on Gut Microbiota, Eating Behaviour and Sensory Function

Inclusion Criteria: * Between 25 and 65 years old * Undergoing either sleeve gastrectomy or Roux-en-Y gastric bypass * With grade 3 obesity (BMI≥40 kg/m²) or with BMI≥35 kg/m² and at least one comorbidity likely to be improved after surgery, with the exception of type 2 diabetes * Signed consent form * Living less than an hour and 30 minutes from the hospital * Presence of effective and stable contraception for women of childbearing potential Exclusion Criteria: * Type 2 diabetes * Presence of a contraindication to bariatric surgery * Presence of gastrointestinal pathologies with an inflammatory component, known gastroparesis, total gastrectomy, colectomy, exocrine pancreatic insufficiency, known endocrine pathologies inducing hyperglycaemia (uncontrolled dysthyroidism, acromegaly, hypercorticism, etc.), severe chronic renal insufficiency (\< 30mL/min), or hepatocellular insufficiency * Claustrophobic * Pregnant or breastfeeding women * Taking an obesity treatment 3 months before surgery * Taking a corticoids, immunosuppression, anabolizing, or growing hormones, antibody treatments less than 3 months before inclusion * Daily taking of laxatives or drugs that can strongly interfere with the composition of the intestinal microbiota. If taken sporadically, the patient can be included at a distance (3 weeks) from the laxatives taken. * Specific diets (vegetarian, vegan or without gluten) * No French speaker * Already included in other study * Donated blood in the last two months * Without freezer access * With allergy or intolerance to food propose in ad libitum buffet