Body-composition differences between African American and white women: relation to resting energy requirements

• Published in: The American journal of clinical nutrition Vol. 79; no. 5; pp. 780 - 786
• Main Authors: Jones, A. Jr, Shen, W, St-Onge, M.P, Gallagher, D, Heshka, S, Wang, Z.M, Heymsfield, S.B
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01.05.2004; American Society for Clinical Nutrition, Inc
• Subjects: Adipose Tissue - metabolism; Adult; African Americans; Basal Metabolism - physiology; Biological and medical sciences; Black or African American - genetics; Body Composition - genetics; Body Composition - physiology; Body Weight - physiology; Bone and Bones - metabolism; Cohort Studies; Energy Metabolism - physiology; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; Humans; Magnetic Resonance Imaging - methods; Metabolism; Middle Aged; Muscle, Skeletal - metabolism; Nutrition; Obesity; Tomography, X-Ray Computed - methods; Vertebrates: anatomy and physiology, studies on body, several organs or systems; White people; White People - genetics; Women; Human; Obesity; Nutrition disorder; Energy requirements; Body composition; Energy requirement; White; Female; nutritional assessment; resting metabolic rate; Woman; Nutritional status; African American
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/79.5.780

Background: Body composition differs between African American (AA) and white women, and the resting metabolic rate (RMR) is likely to be lower in AA women than in white women. Objective: We tested 2 hypotheses: that AA women have a greater proportion of low-metabolic-rate skeletal muscle (SM) and bone than do white women and that between-race musculoskeletal differences are a function of body weight. Design: Hypothesis 1 was tested by comparing SM, bone, adipose tissue, and high-metabolic-rate residual mass across 22 pairs of matched AA and white women. Magnetic resonance imaging and dual-energy X-ray absorptiometry were used to partition weight into 4 components, and RMR was both calculated from tissue-organ mass and measured. Hypothesis 2 was evaluated by measuring SM, bone, fat, and residual mass in 521 AA and white women with the use of dual-energy X-ray absorptiometry alone. Results: Hypothesis 1: AA women had greater SM (average +/- SD group difference: 1.52 +/- 2.48 kg; P < 0.01) and musculoskeletal mass (1.72 +/- 2.66 kg; P < 0.01) than did white women. RMR calculated from body composition and measured RMR did not differ; RMR estimated by both approaches tended to be lower (approximately equal to 160 kJ/d) in AA women than in white women. Hypothesis 2: SM was significantly correlated with weight, height, age, and race x weight interaction; greater SM in the AA women was a function of body weight. Conclusions: Lower RMRs in AA women than in white women are related to corresponding differences in the proportions of heat-producing tissues and organs, and these race-related body-composition differences increase as a function of body weight.