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


METHODS
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 ( +/- 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 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.
Jones
Alfredo
A
Department of Medicine, Obesity Research Center, St Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, Weight Control Unit, 1090 Amsterdam Avenue, 14th Floor, New York, NY 10025, USA.
Shen
Wei
W
St-Onge
Marie-Pierre
MP
Gallagher
Dympna
D
Heshka
Stanley
S
Wang
ZiMian
Z
Heymsfield
Steven B
SB
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D001741:Black or African American / Q000235:genetics; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition / Q000235:genetics / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D014057:Tomography, X-Ray Computed / Q000379:methods; D044465:White People / Q000235:genetics