Introduction Only a few randomized clinical trials (RCTs) have reported 5-year outcomes of sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) and they have used different study designs based on various hypothesis frameworks, including superiority, equivalence, and noninferiority. The aim of this study was to highlight the impact of study design on the interpretation of 5-year weight loss outcomes of SG versus RYGB. Methods PubMed, Embase and Cochrane databases were searched for RCTs comparing 5-year weight loss between SG and RYGB with follow-up rate exceeding 70% using percentage excess weight loss (%EWL) or percentage total weight loss (%TWL) through January 20, 2026. The revised Cochrane risk-of-bias tool for randomized trials (RoB 2) was used to assess the risk of bias. A pooled synthesis of weight loss was performed using a fixed-effects model and unstandardized mean differences were used to measure the effect size. Results Four European studies met the inclusion criteria with a total of 975 patients: two superiority trials and two equivalence trials. The risk of bias was assessed to be low in all four studies. The pooled estimates indicate that %EWL was 8.5 (95%CI 5.4 to 11.6) and %TWL 3.6 (95%CI 2.4 to 4.9) percentage points higher in RYGB compared with SG. Conclusions The results across the four studies were highly consistent showing greater weight loss after RYGB compared with SG. Whether this difference should be interpreted as clinically relevant or whether the procedures may be considered equivalent depends on the predefined hypothesis.
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Hurme et al. (2026) studied this question.
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