Bariatric Surgery Versus Diet Alone in the Bile Acid Pathway and Weight Loss

Inclusion Criteria: * Women of childbearing potential will have negative pregnancy tests within 48 hours of enrolment. * BMI: ≥ 40 * Individuals who have elected to have RYGB at the Mayo Clinic Bariatric Center of Excellence, and individuals with a BMI ≥40 who are otherwise healthy with controlled cardiac, pulmonary, gastrointestinal, hepatic, renal, hematological, neurological, or endocrine disorders. The RYGB participants will be invited to participate when their surgery is scheduled at the Mayo Clinic Bariatric Center of Excellence. * The non-RYGB participants (BMI ≥40) will be otherwise healthy individuals with no unstable psychiatric disease and no unstable cardiac, pulmonary, gastrointestinal, hepatic, renal, hematological, neurological, or endocrine disorders. Exclusion Criteria: * History of abdominal surgery including cholecystectomy and other than appendectomy, Caesarian section or tubal ligation. * Positive history of chronic gastrointestinal diseases, or systemic disease that could affect gastrointestinal motility, or use of medications that may alter gastrointestinal motility, appetite or absorption, e.g., orlistat, phentermine. * Significant untreated psychiatric dysfunction based upon screening with the Hospital Anxiety and Depression Inventory (HAD), a self-administered alcoholism screening test (AUDIT-C) and the Questionnaire on Eating and Weight Patterns (binge eating disorders and bulimia). If such a dysfunction is identified by a depression or anxiety s…