Resting Energy Expenditure and Organ-Tissue Body Composition 5 Years After Bariatric Surgery
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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.
We compared REE and body composition of African-American and Caucasian Roux-en-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.
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/day, p = 0.20); year 2 (− 27.9 ± 37.3 kcal/day, p = 0.46); year 5 (114.6 ± 42.3 kcal/day, 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/day, p = 0.8; − 46.9 ± 64.9 kcal/day, p = 0.47; 47.7 ± 83.0 kcal/day, p = 0.57, at years 1, 2, and 5, respectively).
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 levels.
Clinical Trial Registration
Long-term Effects of Bariatric Surgery (LABS-2) NCT00465829
KeywordsBariatric surgery Roux-en-Y gastric bypass Resting energy expenditure Body composition Fat-free mass Skeletal muscle Organs Brain
This study was supported by the National Institutes of Health grants RO1-DK-72507, P30-DK-26687, and T32-DK007559 (supported TL, EW, and LD).
Compliance with Ethical Standards
Procedures performed in studies involving human participants were approved by the Institutional Review Boards of the relevant institutions and were in accordance with the ethical standards of the institutions and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Conflict of Interest
Nerys M. Astbury declares having been supported by a research grant from the Cambridge Weight Plan UK Ltd to the University of Oxford. Also, the terms of Nerys M. Astbury’s support require that the following statement be included in the paper: “Nerys M. Astbury is supported by funding from the National Institute for Health Research (NIHR), Oxford Biomedical Research Centre (BRC). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.”
The remaining authors declare that they have no conflict of interest.
Written informed consent was obtained from all individual participants included in the study.
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