Systematic review of five-year outcomes after one-anastomosis gastric bypass

One-anastomosis gastric bypass (OAGB) has emerged as a simplified bariatric procedure that has gained global popularity due to its technical efficiency and favorable outcomes. While short-term results regarding weight loss and comorbidity resolution are well established, its long-term safety and efficacy remain subjects of ongoing debate. This systematic review aimed to evaluate 5-year postoperative outcomes of OAGB as a primary bariatric procedure. A comprehensive literature search was performed in PubMed on January 30, 2025, following PRISMA guidelines. Eligible studies included adults with body mass index (BMI) ≥ 35 kg/m² undergoing OAGB as a primary operation with reported 5-year outcomes. From 725 records initially identified, seven studies met inclusion criteria, encompassing 5524 patients at baseline and 3735 with complete 5-year follow-up. Across studies, the weighted mean age was 38.3 years and 73% of patients were female. At 5 years, OAGB achieved a mean BMI of 30.1 kg/m², a mean total weight loss of 33.2%, and a mean excess weight loss of 74.2%. Reported remission rates of obesity-related comorbidities were 77.4% for type 2 diabetes, 58.0% for hypertension, 71.9% for dyslipidemia, and 86.6% for obstructive sleep apnea. Long-term complications included marginal ulcers, gastroesophageal reflux, anemia, and hypoalbuminemia, although their incidence varied and only a minority of cases required revisional surgery. Importantly, no procedure-related mortality was observed. Overall, the available evidence remains limited, heterogeneous, and sometimes conflicting. Some studies suggest the possibility of sustained weight loss and metabolic improvement at 5 years; however, the quality and consistency of the data preclude firm conclusions. While short- to mid-term outcomes have been reported, the long-term safety profile-particularly regarding nutritional deficiencies and bile reflux-remains insufficiently characterized. Therefore, OAGB cannot currently be considered superior or equivalent to other malabsorptive procedures, and reliable comparative conclusions with techniques such as RYGB or single-anastomosis duodenoileal bypass with sleeve gastrectomy cannot yet be established.