Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle

Am J Hum Biol. 2001 Sep-Oct;13(5):612-9. doi: 10.1002/ajhb.1099.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acquired Immunodeficiency Syndrome / physiopathology
  • Adipose Tissue / anatomy & histology
  • Adipose Tissue / physiology
  • Adult
  • Age Factors
  • Aged
  • Body Composition*
  • Body Weight
  • Female
  • Humans
  • Magnetic Resonance Imaging*
  • Male
  • Middle Aged
  • Muscle, Skeletal / anatomy & histology*
  • Muscle, Skeletal / physiology*
  • Regression Analysis
  • Sex Characteristics