Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle.
Muscularity, or the proportion of adipose tissue-free body mass (ATFM) as skeletal muscle (SM), provides valuable body composition information, especially for age-related SM loss (i.e., sarcopenia). Limited data from elderly cadavers suggest a relatively constant SM/ATFM ratio, 0.540 +/- 0.046 for men (mean +/- SD, n = 6) and 0.489 +/- 0.049 for women (n = 7). The aim of the present study was to examine the magnitude and constancy of the SM/ATFM ratio in healthy adults. Whole-body SM and ATFM were measured using multi-scan magnetic resonance imaging. The SM/ATFM ratio was 0.528 +/- 0.036 for men (n = 139) and 0.473 +/- 0.037 for women (n = 165). Multiple regression analysis indicated that the SM/ATFM ratio was significantly influenced by sex, age, body weight, and race. The four factors explained 50% of the observed between individual variation in the SM/ATFM ratio. After adjusting for age, body weight, and race, men had a larger SM/ATFM ratio than women. Both older men and women had a lower SM/ATFM ratio than younger subjects, although the relative reduction was greater in men. After adjustment for sex, age, and body weight, there were no significant differences in the SM/ATFM ratios between Asian, Caucasian, and Hispanic subjects. In contrast, African-American subjects had a significantly greater SM/ATFM ratio than subjects in the other three groups. In addition, the SM/ATFM ratio was significantly lower in AIDS patients than corresponding values in healthy subjects.
Wang
Z
Z
Obesity Research Center, St. Luke's-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, New York, USA. ZW28@Columbia.edu
Heo
M
M
Lee
R C
RC
Kotler
D P
DP
Withers
R T
RT
Heymsfield
S B
SB
D000163:Acquired Immunodeficiency Syndrome / Q000503:physiopathology; D000273:Adipose Tissue / Q000033:anatomy & histology / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000368:Aged; D001823:Body Composition; D001835:Body Weight; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D012044:Regression Analysis; D012727:Sex Characteristics