Background

Weight loss following bariatric surgery is highly variable and whether sex differences exist remain unclear as >80% of patients are women. Pre-clinical studies demonstrate numerous sex-specific responses to bariatric surgery, though no such effects have been reported clinically.

Methods

Total weight loss (percent) over time following RYGB (n=3700) and VSG (n=1221) was modeled up to 5 years at a single academic center from a retrospective, observational cohort. Modeled estimates were adjusted for known clinical confounders (age, preoperative body weight, procedure type (RYGB, VSG), race, and presence of insulin resistance/diabetes).

Results

Percent total weight loss demonstrated a strong sex by procedure interaction, with women having a significant weight loss advantage with RYGB compared to VSG [adjusted difference at 5-years: 7.35% (95% CI: 6.11,8.60); P<0.0001]. Men showed similar weight loss with RYGB or VSG (adjusted difference at 5-years: 0.25% (-1.87,2.36); P=0.82; P-interaction between sex and procedure type=0.0001]. Women experienced greater weight loss than men, and RYGB had greater weight loss than VSG [adjusted difference at 5-years: 3.66 (2.53,4.79) and 5.63% (4.55,6.70), respectively; both P<0.0001]. Expectedly, increasing age, preoperative weight, and diabetes were associated with less weight loss. Follow up characteristics were similar across sex and operation.

Conclusions

Weight loss after bariatric surgery is sexually dimorphic and operation-dependent. These factors affect patient expectations, procedure selection, risk/benefit ratio, and possibly other long-term outcomes. Further studies are needed to corroborate these potential effects and their long-term implications.