What is Weight Loss after Bariatric Surgery Expressed in Percentage Total Weight Loss (%TWL)? An Updated Systematic Review

Percentage total weight loss (%TWL) is a robust and widely used outcome measure for assessing weight loss after metabolic and bariatric surgery (MBS). This study is an update of the 2021 systematic review on weight loss after MBS expressed in %TWL, now including results of one anastomosis gastric bypass (OAGB), Roux-en-Y gastric bypass (RYGB), and sleeve gastrectomy (SG). A total of 4,541 records were screened, and 49 studies were included, comprising both cohort and registry-based data. Descriptive pooled estimates suggested that OAGB was associated with the highest nadir %TWL within the first two years, whereas nadir %TWL appeared comparable between RYGB and SG. During longer-term follow-up, OAGB appeared to maintain a higher pooled mean %TWL than RYGB and SG. These findings should be interpreted cautiously given the heterogeneity of included studies and the limited availability of long-term data. They should be balanced against long-term complications and need for revisional surgery, which were beyond the scope of the present review. Standardized reporting and high-quality studies with extended follow-up using %TWL as the primary outcome are needed to improve comparability and interpretation of long-term weight loss after bariatric surgery.