Prospective Evaluation of Stapled Intact-Duodenum Bipartition With Sleeve Gastrectomy (SIBS)

Inclusion Criteria * Age 18-65 years. * Body mass index (BMI) ≥35 kg/m², regardless of the presence or severity of obesity-associated medical conditions; or BMI 30.0-34.9 kg/m² with type 2 diabetes mellitus or another clinically significant obesity-associated medical condition and inadequate weight loss or improvement following appropriate nonsurgical management. * Eligible for metabolic and bariatric surgery following multidisciplinary clinical assessment. * Considered suitable for laparoscopic Stapled Intact-Duodenum Bipartition with Sleeve Gastrectomy (SIBS) based on preoperative assessment. * For primary procedures, no previous metabolic or bariatric surgical procedure. * For revisional procedures, previous sleeve gastrectomy with a clinical indication for revisional metabolic/bariatric surgery and anatomy considered suitable for SIBS. * Able to understand the investigational nature of the SIBS procedure, its potential risks and benefits, and established alternative bariatric procedures. * Able and willing to provide written informed consent. * Willing and able to comply with the scheduled postoperative clinical, nutritional, laboratory, and study follow-up for at least 12 months. Exclusion Criteria * Age \<18 years or \>65 years. * Pregnancy or breastfeeding. * Planned pregnancy during the 12-month postoperative study period. * Contraindication to general anesthesia or laparoscopic metabolic/bariatric surgery. * Previous gastrointestinal surgery resulting in anatomy that precludes safe performance of the planned SIBS procedure, except previous sleeve gastrectomy in participants undergoing an eligible revisional procedure. * Intraoperative anatomy that prevents safe creation of a tension-free side-to-side duodenoileal anastomosis. * Active inflammatory bowel disease involving the small intestine. * Active gastrointestinal malignancy or other active malignancy for which the proposed operation or follow-up would be inappropriate. * Severe hepatic dysfunction, severe renal dysfunction, or another major systemic illness considered to confer an unacceptable operative or nutritional risk. * Pre-existing severe protein-calorie malnutrition or clinically significant nutritional deficiency that cannot be adequately corrected before surgery. * Active gastrointestinal ulceration or another gastrointestinal condition considered to substantially increase the risk of the planned procedure. * Uncontrolled psychiatric illness or cognitive impairment that precludes valid informed consent or adherence to postoperative care. * Active alcohol or substance use disorder considered incompatible with safe metabolic and bariatric surgery. * Inability or unwillingness to adhere to postoperative dietary recommendations, nutritional supplementation, or scheduled follow-up. * Any medical, surgical, anatomical, or psychosocial condition that, in the judgment of the multidisciplinary bariatric team, makes participation or performance of SIBS inappropriate or unsafe.