Preoperative BMI and Five-Year Proportional Weight-Loss Maintenance After Roux-en-Y Gastric Bypass: A Retrospective Cohort Study

Introduction: Roux-en-Y gastric bypass (RYGB) produces substantial weight loss, but long-term proportional maintenance varies. We examined whether preoperative body mass index (BMI) category was associated with change in percentage total weight loss (%TWL) between 12 and 60 months after primary RYGB. Methods This retrospective cohort study included adults with preoperative BMI ≥ 35 kg/m² who underwent primary RYGB between January 2016 and March 2021 and had weight data at 12 and 60 months. Of 456 eligible patients, 113 (24.8%) lacked 12- or 60-month data and were lost to follow-up (343 analyzed). The primary outcome was Δ%TWL 12–60 (60-month minus 12-month %TWL), analyzed by linear regression before and after adjustment for age, sex, preoperative type 2 diabetes, and 12-month %TWL. Results Among 343 patients, mean Δ%TWL 12–60 was − 3.2, − 5.9, and − 5.4 percentage points across ascending BMI categories. Adjusted differences versus BMI 35–<40 kg/m² were − 2.09 points for BMI 40–<45 kg/m² (95% CI, − 4.62 to 0.44) and − 1.57 points for BMI ≥ 45 kg/m² (95% CI, − 4.18 to 1.03; global P=.268). At 60 months, mean %TWL was 28.7%, 28.3%, and 28.9%, whereas mean BMI was 27.2, 30.4, and 33.6 kg/m². Conclusion Preoperative BMI category was not clearly associated with %TWL change from 12 to 60 months after RYGB, although the confidence intervals included between-category differences of several percentage points. Similar 5-year %TWL coexisted with substantially different attained BMI values; both measures may therefore provide complementary anthropometric information.