Less-than-expected weight loss in normal-weight women undergoing caloric restriction and exercise is accompanied by preservation of fat-free mass and metabolic adaptations

Authors

Karsten Koehler, University of Nebraska - LincolnFollow
M. J. De Souza, The Pennsylvania State UniversityFollow
N. I. Williams, The Pennsylvania State UniversityFollow

Date of this Version

2017

Citation

Published in European Journal of Clinical Nutrition 71 (2017), pp. 365–371. doi:10.1038/ejcn.2016.203

Comments

Copyright © 2017 Macmillan Publishers Limited, part of Springer Nature. Used by permission.

Abstract

Background/Objectives: Normal-weight women frequently restrict their caloric intake and exercise, but little is known about the effects on body weight, body composition and metabolic adaptations in this population.

Subjects/Methods: We conducted a secondary analysis of data from a randomized controlled trial in sedentary normal-weight women. Women were assigned to a severe energy deficit (SEV: –1062 ± 80 kcal per day; n = 9), a moderate energy deficit (MOD: –633 ± 71 kcal per day; n = 7) or energy balance (BAL; n = 9) while exercising five times per week for 3 months. Outcome variables included changes in body weight, body composition, resting metabolic rate (RMR) and metabolic hormones associated with energy conservation.

Results: Weight loss occurred in SEV (–3.7 ± 0.9 kg, P<0.001) and MOD (–2.7 ± 0.8 kg; P = 0.003), but weight loss was significantly less than predicted (SEV: –11.1 ± 1.0 kg; MOD: –6.5 ± 1.1 kg; both P<0.001 vs actual). Fat mass declined in SEV (P<0.001) and MOD (P = 0.006), whereas fat-free mass remained unchanged in all groups (P40.33). RMR decreased by − 6 ± 2% in MOD (P = 0.020). In SEV, RMR did not change on a group level (P = 0.66), but participants whose RMR declined lost more weight (P = 0.020) and had a higher baseline RMR (P = 0.026) than those whose RMR did not decrease. Characteristic changes in leptin (P = 0.003), tri-iodothyronine (P = 0.013), insulin-like growth factor-1 (P = 0.016) and ghrelin (P = 0.049) occurred only in SEV. The energy deficit and adaptive changes in RMR explained 54% of the observed weight loss.

Conclusions: In normal-weight women, caloric restriction and exercise resulted in less-than-predicted weight loss. In contrast to previous literature, weight loss consisted almost exclusively of fat mass, whereas fat-free mass was preserved.