BackgroundAccording to several short-term studies, single-anastomosis sleeve ileal (SASI) bypass offers similar weight loss to Roux-en-Y Gastric Bypass (RYGB) with fewer complication and better comorbidity reduction/resolution. Long-term data on this operation is lacking in the literature. The purpose of this study was to analyze the outcomes of SASI bypass up to 4 years.MethodsThis study is a retrospective cohort analysis of 366 patients with morbid obesity who underwent primary SASI bypass from January 2018 to February 2022.ResultsThe mean age and preoperative body mass index (BMI) were 41 years (range 22–71 years) and 43.9 ± 6.5 kg/m2, respectively. Follow-up was available for 229 patients at 1-year (89%), 112 patients at 2-year (75%), 61 patients at 3-year (75%), and 35 patients at 4-year (71%). The intraoperative, short-term, and long-term complication rates were 0%, 2.5%, 4.6%, respectively. After 4 years, mean percentage excess weight loss (%EWL) was 93.3% and total weight loss (%TWL) was 41.2%. Remission of comorbidities was 93% for type 2 diabetes mellitus, 73% for hypertension, 83% for hyperlipidemia, 79% for sleep apnea, and 25% for gastroesophageal reflux disease (GERD). Biliary gastritis and ulcers are seldom. Eight patients developed de novo GERD symptoms requiring proton pump inhibitor treatment. None of the patients in our study had hypoalbuminemia or malabsorption that did not respond to increased protein intake and vitamin or mineral supplementation.ConclusionSASI bypass appears to be safe, and one of the most effective bariatric procedures regarding weight loss and obesity related comorbidities. The double-outlet created in this procedure seemingly minimizes nutritional complications.Graphical abstract