Resting Energy Expenditure and Organ-Tissue Body Composition 5 Years After Bariatric Surgery

Abstract

Introduction: Bariatric surgery induced weight loss may reduce resting energy expenditure (REE) and fat-free mass (FFM) disproportionately thereby predisposing patients to weight regain and sarcopenia. Methods:We compared REE and body composition of African-American and Caucasian Rouxen-Y gastric bypass (RYGB) patients after surgery with a group of non-operated controls (CON). REE by indirect calorimetry; skeletal muscle (SM), trunk organs and brain volumes by MRI; and FFM by DXA, were measured at post-surgery visits and compared with CON (N=84) using linear regression models that adjusted for relevant covariates. Ns in RYGB were 50, 42, and 30 for anthropometry and 39, 27, 17 for MRI body composition at years 1, 2 and 5 after surgery, respectively.Results: Regression models adjusted for age, weight, height, ethnicity, and sex showed REE differences (RYGB minus CON; mean±s.e.): year 1 (43.2±34 kcal/d, p=0.20); year 2 (-27.9±37.3 kcal/d, p=0.46); year 5 (114.6 ±42.3 kcal/d, p=0.008). Analysis of FFM components showed that RYGB had greater trunk organ mass (~0.4 kg) and less SM (~1.34 kg) than CON at each visit. REE models adjusted for FFM, SM, trunk-organs, and brain mass showed no between group differences in REE (-15.9 ± 54.8 kcal/d, p=0.8; -46.9±64.9 kcal/d, p=0.47; 47.7±83.0 kcal/d, p=0.57, at years 1, 2 and 5, respectively). Conclusions:Post bariatric surgery patients maintain a larger mass of high-metabolic rate trunk organs than non-operated controls of similar anthropometrics. Interpreting REE changes after weight loss requires an accurate understanding of fat-free mass composition at both the organ and tissue level.

Is There a Contribution of Structural Brain Phenotypes to the Variance in Resting Energy Expenditure before and after Weight Loss in Overweight Females?

“…After weight loss, GM added to the variances of REE and REE on FFM residuals, and influenced the body-brain energy allocation. Our data are in line with more recent data obtained in obese patients before and after two years after bariatric surgery [36]. The results showed no impact of weight loss on adjusted REE and brain mass [36].…”

Long-term body composition improvement in post-menopausal women following bariatric surgery: a cross-sectional and case–control study

“…Yet, the menopausal status was not reported. Other studies with similar design found no significant difference in body composition between groups (22,23,39).…”

Mechanisms of Weight Loss After Obesity Surgery

“…Enhanced energy expenditure after obesity surgery may be a contributing mechanism to weight loss. Resting energy expenditure has been measured in humans following RYGB, and most recent studies using indirect calorimetry show resting energy expenditure to either decrease within the first post-operative year [56][57][58] , remain stable 59 or even slightly increase 60 . These changes are reported to be highly dependent on organ-tissue body composition as RYGB patients maintain a larger high-metabolic rate organ mass than non-operated controls 59 .…”

“…Resting energy expenditure has been measured in humans following RYGB, and most recent studies using indirect calorimetry show resting energy expenditure to either decrease within the first post-operative year [56][57][58] , remain stable 59 or even slightly increase 60 . These changes are reported to be highly dependent on organ-tissue body composition as RYGB patients maintain a larger high-metabolic rate organ mass than non-operated controls 59 . Moreover, the acute weight loss following obesity surgery was found to affect the accuracy of energy expenditure predictive equations 61 .…”