Proportion of adipose tissue-free body mass as skeletal muscle: Magnitude and constancy in men

Although it is often assumed that skeletal muscle (SM) is a fixed proportion of adipose tissue-free body mass (ATFM), there is little data in living humans that supports this hypothesis. Limited data from elderly cadavers suggests a relatively constant proportion of ATFM as SM in men (mean ± SD, 0.540 ± 0.046) and women (0.489 ± 0.049). The present study tested the hypothesis that SM is a relatively constant proportion of ATFM in healthy men. Whole body SM and ATFM were measured using multiscan computerized axial tomography. The SM/ATFM ratio in the men (n = 24) was 0.563 ± 0.036 which was not significantly different from the value found in the elderly male cadavers. Multiple regression analysis indicated that the SM/ATFM ratio was significantly related to 1/ATFM (P = 0.036) and the body mass index (P = 0.024), and not with age. Further study is needed of other possible factors such as physical activity, gender, race, and disease state, that may effect the relationship between SM and ATFM. Am. J. Hum. Biol. 9:487-492, 1997. © 1997 Wiley-Liss, Inc.