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

• Published in: European journal of clinical nutrition 2017-03, Vol.71 (3), p.365-371
• Main Authors: Koehler, K, De Souza, M J, Williams, N I
• Format: Article
• Language: English
• Subjects: 692/699/2743; Adaptation; Adolescent; Adult; Basal Metabolism; Bioenergetics; Body Composition; Body fat; Body Mass Index; Body weight; Body weight loss; Caloric Restriction; Clinical Nutrition; Diet; Dietary Carbohydrates - administration & dosage; Dietary Fats - administration & dosage; Dietary Proteins - administration & dosage; Dietary restrictions; Energy balance; Energy conservation; Epidemiology; Exercise; Fat-free; Fat-free body mass; Female; Ghrelin; Growth factors; Health aspects; Hormones; Humans; Insulin; Insulin-like growth factor I; Internal Medicine; Leptin; Low calorie diet; Medicine; Medicine & Public Health; Metabolic Diseases; Metabolic rate; Metabolism; original-article; Patient Compliance; Public Health; Retrospective Studies; Secondary analysis; Weight control; Weight Loss; Womens health; Young Adult
• ISSN: 0954-3007; 1476-5640
• DOI: 10.1038/ejcn.2016.203

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 ( P >0.33). 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.