Extensive weight loss prior to bariatric surgery is associated with worse outcomes

Background : Weight loss has been shown to favorably affect obesity-related comorbid disease. Prior studies have shown that a 10% preoperative weight loss is associated with fewer complications after gastric bypass surgery. Although the optimal preoperative preparation for bariatric surgery is not standardized, prerequisite weight loss prior to bariatric surgical procedures is often mandated, typically around 10%, and includes a calorie-restrictive preoperative diet. Objectives : To evaluate the association between extensive preoperative weight loss and perioperative outcomes in patients undergoing bariatric surgery. Methods : To determine optimal weight loss prior to bariatric surgery, we compared patients who lost over 10% of their highest weight preoperatively to patients who did not within the MBSAQIP database from 2015-2021, which included over 1.3 million patients. Results : Patients who lost more than 10% of their highest preoperative weight were more likely to experience postoperative complications, including reoperation (1.40% vs 1.21%, p<.001), bleeding (0.85% vs 0.67%, p<.001), emergency department visits (7.11% vs 6.57%, p<.001), and dehydration (3.92% vs 3.61%, p<.001). These differences remained significant with multivariable regression analysis controlling for multiple patient factors and procedure type. Patients who lost more than 10% of their highest preoperative weight were also found to have a lower mortality (0.10% vs 0.08%, p=.04) and readmission (3.92% vs 3.60%, p<.001), however on multivariable regression analysis these findings were not found to be statistically significant. Conclusion : While preoperative weight loss prior to bariatric surgery may be beneficial, , over 10% preoperative weight loss is associated with worse outcomes and should be avoided.