BACKGROUND: Roux-en-Y gastric bypass (RYGB) is widely regarded as a cornerstone intervention for individuals afflicted with metabolic syndromes and severe obesity. However, one anastomosis gastric bypass (OAGB) emerged after RYGB as a more straightforward and less technically demanding operation. This systematic review and meta-analysis aims to compare both procedures and update the currently existing evidence. METHODS: We systematically searched PubMed, Scopus, and the Cochrane Central Register for randomized controlled trials (RCTs) that compared OAGB with RYGB as primary operations. RESULTS: Twelve studies were included in this meta-analysis, with a total of 904 patients. Total weight loss percentage (TWL%) was statistically higher in the OAGB group at 6 months (95% CI 0.80 to 2.94
P = 0.006) with no differences in 12, 24, and 36 months compared to RYGB. On the other hand, OAGB exhibited a significantly higher excess weight loss percentage (EWL%) compared to RYGB at 12 months (95% CI 3.08 to 9.73
P = 0.0002). EWL% was comparable in both procedures at 6, 24, and 60 months of follow-up. There were no statistically significant differences in terms of the resolution of comorbidities related to obesity. De novo gastro-esophageal reflux disease (GERD) (RR 2.58
95% CI 1.55 to 4.3
P = 0.0003) and marginal ulcers (RR 2.7
95% CI 1.07 to 6.84
P = 0.04) were significantly higher in patients who underwent OAGB in comparison to RYGB. CONCLUSIONS: In conclusion, OAGB is comparable to RYGB in terms of weight loss parameters and comorbidity resolution. However, OAGB can lead to a higher risk of development of marginal ulcers and de novo GERD.