Single-anastomosis duodenoileal bypass versus one-anastomosis gastric bypass: 1-year results of the OASIS randomized trial.

BACKGROUND: Single-anastomosis duodenoileal bypass with sleeve gastrectomy (SADI-S) and one-anastomosis gastric bypass (OAGB) are increasingly used bariatric procedures, but high-quality comparative evidence remains limited. OBJECTIVES: To compare 1-year efficacy and safety outcomes of SADI-S and OAGB as primary bariatric procedures in patients with severe obesity. SETTING: Secondary care bariatric surgery center. METHODS: This was a single-center, prospective, randomized, single-blind controlled trial. Ninety-nine patients aged 18-65 years with body mass index (BMI) 45-50 kg/m2 were enrolled between 2023 and 2024; 90 underwent surgery (43 SADI-S; 47 OAGB). Patients were randomly assigned (1:1) using a computer-generated sequence. The primary outcome was excess weight loss (EWL) at 1 year. The secondary outcomes included total weight loss (TWL), BMI, late complications (>30 days), comorbidity resolution, nutritional deficiencies, and quality of life. RESULTS: At 1 year, no significant differences were observed between groups in EWL (84.34% vs 79.61%; P = .209), TWL (35.85% vs 33.02%; P = .075), or BMI (27.93 vs 28.92 kg/m2; P = .168). Comorbidity resolution rates were comparable. Nutritional deficiencies were infrequent (7.3% vs 4.3%; P = .878), with all cases related to iron deficiency. Late complications were significantly more frequent after OAGB (35.4% vs 7.1%; P = .0003), mainly related to bile reflux and managed conservatively or endoscopically. SADI-S was associated with fewer complications but included two cases requiring surgical reintervention. One death occurred in the SADI-S group and was not directly attributable to the procedure. Quality of life improved similarly in both groups. CONCLUSIONS: SADI-S and OAGB achieved comparable weight loss and metabolic outcomes at 1 year in patients with BMI 45-50 kg/m2 but showed distinct complication profiles. OAGB was associated with a higher rate of bile reflux-related events, whereas SADI-S had fewer but more severe complications. These findings support an individualized approach to procedure selection. Longer-term follow-up is required.