Setting realistic expectations for weight loss after laparoscopic sleeve gastrectomy

Introduction
Despite the clinical benefits of bariatric surgery, some patients have experienced disappointment with their weight loss. Setting realistic expectations is the key to success.

Aim
To develop a specific prediction calculator to estimate the expected body mass index (BMI) at 1 year after laparoscopic sleeve gastrectomy (LSG).

Material and methods
A retrospective analysis was performed to study 211 patients after primary LSG. Nine baseline variables were analyzed. Least angle regression (LARS) was employed for variable selection and to build the predictive model. External validation was performed on a dataset of 184 patients. To test the accuracy of the model, a Wilcoxon signed-rank test was performed between BMI estimates and the observed BMI. A linear logistic equation was used to construct the online predictive calculator.

Results
The model included three variables – preoperative BMI ( = 0.023, p < 0.001), age ( = 0.005, p < 0.001), and female gender ( = 0.116, p = 0.001) – and demonstrated good discrimination (R2 = 0.672; adjusted R2 = 0.664) and good accuracy (root mean squared error of estimate, RMSE = 0.124). The difference between the observed BMI and the estimated BMI was not statistically significant (median = 0.737 (–2.676, 3.254); p = 0.223). External validation confirmed good performance of the model.

Conclusions
The study revealed a useful predictive model for estimating BMI at 1 year after LSG. The model was used for development of the PREDICT BMI calculator. This tool allows one to set realistic expectations of weight loss at one year after LSG.