One anastomosis gastric bypass (OAGB): a scoping review

BACKGROUND: Obesity has become a global health crisis, with bariatric surgery being among the most effective interventions for treatment-resistant obesity. One Anastomosis Gastric Bypass (OAGB) has gained popularity for its technical simplicity and promising outcomes. However, concerns remain regarding long-term complications, especially bile reflux and gastroesophageal reflux disease (GERD). This scoping review aimed to synthesize the current literature on OAGB, focusing on four domains: percentage excess weight loss (%EWL), remission of metabolic and cardiovascular conditions, postoperative complications, and incidence of GERD. METHODS: A systematic search was conducted in PubMed, Embase, and Web of Science (May 2025). We included randomized and non-randomized trials, systematic reviews, meta-analyses, and observational studies that reported at least one of the target outcomes in adults undergoing OAGB. Case reports, narrative reviews, case series, and retracted studies were excluded. Screening was performed using the Active Learning for Systematic Reviews (ASReview) tool. Data were charted narratively and summarized in tables. Definitions of outcomes and surgical variations were recorded where available. Risk of bias in novel randomized controlled trials was assessed using Cochrane's RoB 2.0 tool. RESULTS: Sixty-seven studies were included out of 3791 records screened. OAGB showed higher or comparable %EWL versus Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and SADI-S, particularly in short- and mid-term follow-up. However, there was significant variability in how %EWL was defined and calculated, including inconsistent or absent definitions of ideal weight. Type 2 diabetes remission ranged from 76.8 to 100%, with meaningful improvements in hypertension, dyslipidemia, and obstructive sleep apnea. GERD incidence varied and was influenced by limb length, presence of hiatal hernia, and surgical technique. Longer biliopancreatic limbs enhanced weight loss but increased nutritional risk. Definitions and reporting of complications varied significantly. CONCLUSIONS: OAGB is an effective metabolic and bariatric procedure with favorable outcomes in weight loss and disease remission. However, heterogeneity in surgical techniques, outome definitions, and limited follow-up time to assess long-term outcomes emphasize the need for standardized reporting and further high-quality long-term studies to guide patient selection and decision making.