This is a pilot open label study that aims to examine the efficacy of biotin supplementation with or without enriched soluble and insoluble fibers given during 3 months before the bariatric surgery, on gut microbiota composition and functional capacity to produce B vitamins (primary outcomes), compared to standard of care (e.g. patient preparation to bariatric surgery).~The study is a 4-arm clinical trial:~Arm 1: patients with usual follow-up (standard of care) receiving during 3 months before the surgery usual general dietary recommendations regarding balanced diet comprising legumes and fruits, meat or equivalent, dairy products and starch and bread Arm 2: Same usual general dietary recommendations PLUS Biotin 450 µg per day (1 capsule per day) during 3 months before the surgery.~Arm 3: Same usual general dietary recommendations PLUS 3 servings per day of PureLean® Fiber, a powdered blend of fibers and prebiotics, during 3 months before the surgery Arm 4: Same usual general dietary recommendations PLUS 3 servings per day of PureLean® Fiber and Biotin 450 µg per day (1 capsule per day), during 3 months before the surgery.~There will be two periods: period 1 during the 3 months before bariatric surgery and period 2 after bariatric surgery (usual standard of care follow-up). The 4 groups will be compared before bariatric surgery and up to 6 months afterward~Patients will receive a schedule of hospitalizations and visits before and after the surgery:~V0: 3 months before surgery~V1: presurgery visit, one day hospitalization~V2: 3 months post-surgery~V3: 6 months post-surgery~At each visit (V0, V1, V2 and V3), will be performed as part of research:~Adipose tissue aspiration~Questionnaires~Fecal samples~Saliva samples (oral microbiota)~Blood samples~Urine samples This planning is part of the standard of care. The same follow-up will be performed in the 4 arms.~Patients will be called 3 times between V0 and V1 by dietician as part of research.
Bariatric surgery improves health outcomes with a maximal weight loss on average occurring 1 year after surgery but with dramatic between-subjects variability in weight loss (ranging from 20 to 160% excess weight loss) for reasons that remain to be elucidated.~The investigators hypothesize that targeting the 3 months pre-surgery period by a calibrated dietary intervention, with fiber enrichment and biotin, will improve gut microbiota richness and subsequently improve subjects' metabolic health that may optimize post bariatric surgery outcomes.~The study is designed as a pilot, comparative, randomized, open-label trial with 4 arms: standard of care, biotin only, fibers only, biotin + fibers.