This randomized clinical trial aims to compare two surgical techniques for the treatment of obesity in patients who also have symptoms of gastroesophageal reflux disease (GERD). The study will compare Nissen-Sleeve Gastrectomy (N-SG)-a sleeve gastrectomy combined with a reflux-preventing procedure-to the Roux-en-Y Gastric Bypass (RYGB), which is the current standard surgical option for obese patients with GERD. Both procedures are widely used to treat severe obesity, but they differ in how they affect the digestive system and the potential for reflux control, nutritional outcomes, and future surgical options. N-SG is a newer technique that preserves the natural pathway of the gastrointestinal tract and allows standard endoscopic access to the bile ducts, which may be beneficial for long-term patient care. RYGB, on the other hand, bypasses part of the stomach and small intestine, which may lead to better reflux resolution but carries risks of nutritional deficiencies and altered anatomy. Eligible participants with obesity and GERD symptoms will be randomly assigned to receive either N-SG or RYGB. The primary goal is to evaluate whether N-SG is not inferior to RYGB in reducing GERD symptoms one year after surgery. Secondary outcomes include weight loss, quality of life, surgical complications, and changes in the hormone ghrelin, which is involved in appetite regulation. In addition, a larger control group of patients without GERD undergoing standard sleeve gastrectomy will be recruited to allow further comparisons. All participants will be followed for one year after surgery, with blood samples, questionnaires, and clinical data collected to assess both metabolic and reflux-related outcomes. This study is being conducted at the University Hospital in Kraków, Poland, and aims to improve the personalization of bariatric treatment for patients suffering from both obesity and reflux.