Objectives: Resting energy expenditure (REE) declines more than what is expected according to body composition changes after caloric restriction. This metabolic adaptation is considered one of the factors favoring weight regain. The aim of this study is to evaluate the changes of REE and calculate the degree of metabolic adaptation occurring after laparoscopic sleeve gastrectomy (LSG).
Methods: REE (by indirect calorimetry) and body composition (fat-free mass or FFM, fat mass or FM by bioelectrical impedance analysis) were determined before and after 12 months in 154 patients with obesity treated with laparoscopic sleeve gastrectomy (LSG).
Results: Weight loss was 29.8 ± 10.6%, with corresponding relative reductions in FM (44.5 ± 22.8%), FFM (13.7 ± 9.9%), and REE (27.3 ± 12.9%). A predictive equation for REE was computed by using the baseline FFM and FM values to account for body composition changes. A predicted post-weight loss REE was calculated by using this equation and entering post-weight loss body composition values. Observed post-surgery REE was significantly lower than predicted one (1410 ± 312 vs 1611 ± 340 kcal/day, P < 0.001) and metabolic adaptation, calculated as the difference between observed and predicted post-weight loss REE, was - 199 ± 238 kcal/day. The post-surgery level of metabolic adaptation was inversely related to postoperative percent weight loss (r = - 0.170; P < 0.05) and FM loss (r = - 0.245; P < 0.01).
Conclusions: A significant reduction of resting energy expenditure and a significant degree of metabolic adaptation both occur after sleeve gastrectomy. A greater metabolic adaptation could be partly responsible for a lower weight loss after surgery.
Keywords: Body composition; Energy expenditure; Laparoscopic sleeve gastrectomy; Metabolic adaptation; Obesity.