Supplementary Material for: Ten-Year Weight Regain After Bariatric Surgery: Prevalence, Predictors, and Metabolic Impact

Introduction: Bariatric surgery (BS) is an effective intervention for severe obesity, but long-term weight regain (WR) can occur and may impact comorbidity outcomes. Methods: In this retrospective study, we analyzed patients who underwent BS with a 10-year follow-up. WR was calculated as the percentage of maximum weight lost (%MWL) that had been regained from the nadir weight. Patients were categorized as "Maintainers" (WR ≤ 20% of %MWL) or "Regainers" (WR > 20%). Results: Among 353 included patients, 317 underwent Roux-en-Y gastric bypass (RYGB) and 36 underwent sleeve gastrectomy (SG), 90.4% were female, with a mean age of 42 ± 11 years and a mean body mass index of 44.6 kg/m². Mean WR at 10 years was 28% (±25), higher in SG vs. RYGB (41.37% vs. 26.17%, p = 0.03). Overall, 56.7% were "Regainers". Baseline type 2 diabetes mellitus (T2D) was associated with an approximately 40% reduced risk of WR > 20% (OR = 0.59; 95% CI: 0.38–0.93; p = 0.023). WR was not significantly associated with the recurrence or remission of T2D, hypertension, or dyslipidemia. Conclusion: WR is common a decade after BS, particularly following SG. While WR does not appear to significantly impact comorbidity recurrence, its clinical relevance warrants further study. Standardized definitions are urgently needed to guide long-term management.