The Effectiveness of Preoperative Liquid Diets on Bariatric Surgery Outcomes

Background Effects of preoperative weight loss on bariatric surgery outcomes have been previously studied, but the true association remains unclear. We aim to determine whether duration of a standardized preoperative liquid diet has significant effects on postoperative outcomes. Methods A retrospective analysis was conducted on 576 patients categorized by preoperative diet duration (2-week vs 4-week). Differences in characteristics were assessed using Pearson Chi-square test for categorical variables and Student’s t-test for independent groups for continuous data. Least squares multivariable linear regression modeling was used to assess predictors of total body weight loss percentage (TBWL%) at 1 year with TBWL% at 30 days and 1 year as primary endpoints. Results Five-hundred and seventy-six patients were analyzed, with 516 undergoing initial bariatric surgery. Ninety-three patients were enrolled in the 2-week liquid diet; 419 patients were enrolled in the 4-week diet. Patients in the 4-week group lost significantly more weight during the preoperative phase ( P < 0.001). There was no difference between 2-week and 4-week diets on TBWL% at 30 days or 1 year. Five-hundred and twelve patients had follow-up at 1 year with age ( P = 0.001) and race ( P < 0.001) of the only significant predictors of TBWL% at 1 year. Conclusion In this retrospective, non-randomized cohort, extending the preoperative liquid diet from 2 to 4 weeks did not result in improved postoperative weight loss at 30 days or 1 year. Age and race were the only significant predictors of TBWL% at 1 year in our cohort, underscoring the importance of patient-level biologic and social determinants.