title: Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle.
abstract: 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.
authors.affiliation: Obesity Research Center, St. Luke's-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, New York, USA. ZW28@Columbia.edu
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Heo
authors.forename: R C
authors.initials: RC
authors.lastname: Lee
authors.forename: D P
authors.initials: DP
authors.lastname: Kotler
authors.forename: R T
authors.initials: RT
authors.lastname: Withers
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: 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