Organic Pollutant Build-Up in Body Fat and Stomach Tissue Linked to Obesity Levels

Inclusion Criteria: * Adults ≥18 years. * BMI ≥30 kg/m² at screening (measured within 30 days before surgery). * Scheduled for primary bariatric surgery (e.g., sleeve gastrectomy or Roux-en-Y gastric bypass) for clinical indications. * Able to provide informed consent. * Willing to allow intraoperative collection of subcutaneous/visceral adipose tissue and gastric tissue for pollutant analysis. * Availability of basic preoperative clinical data (demographics, comorbidities, relevant labs). Exclusion Criteria: * Prior bariatric or major upper gastrointestinal surgery that alters stomach/anatomy relevant to sampling. * Pregnant or breastfeeding at screening or on day of surgery. * Active malignancy (excluding non-melanoma skin cancers) or ongoing systemic immunosuppressive therapy (e.g., chronic corticosteroids, biologics) within 3 months. * Severe organ dysfunction: decompensated cirrhosis (Child-Pugh C) or eGFR \<30 mL/min/1.73m². * Acute infection or decompensated chronic illness that would preclude elective surgery per treating team. * Documented high-level occupational or accidental chemical exposure within 6 months (e.g., pesticide poisoning) likely to bias tissue pollutant measurements. * Participation in another interventional study expected to affect weight or metabolism within 3 months. * Inadequate tissue obtainable at surgery for analysis (determined intraoperatively by the investigators).