Relationship between fat-free mass and urinary excretion of creatinine and 3-methylhistidine in adult humans

J Appl Physiol (1985). 1994 May;76(5):1946-50. doi: 10.1152/jappl.1994.76.5.1946.


The urinary excretion of endogenous creatinine (CRTN) and 3-methylhistidine (3-MH) has been proposed as a predictor of fat-free mass (FFM) in healthy subjects. In this study, we report the relationship between FFM, estimated by densitometry plus deuterium dilution, and daily urinary excretion of CRTN and 3-MH in a sample of 20 healthy adult subjects of both sexes. 3-MH and CRTN were measured in 2 days of urine collection, which followed 4 days of meat-free diet. Meat-free diet was maintained throughout the period of urine collection. The mean of 2 days of excretion of 3-MH was 237.7 +/- 87.3 (SD) and 138.9 +/- 31.2 mumol/day in men and women, respectively. The mean CRTN excretion was 1.51 +/- 0.22 and 0.98 +/- 0.15 g/day in men and women, respectively. CRTN excretion was found well associated with FFM (R2 = 0.89; P < 0.0001), whereas 3-MH was lightly associated with FFM (R2 = 0.33; P < 0.01). Residuals from the regression of 3-MH vs. FFM were found to be correlated with CRTN excretion and FFM (R2 = 0.57 and 0.67, respectively), suggesting that muscularity and the absolute amount of lean mass are relevant for the error in predicting FFM from 3-MH excretion. Data confirm that urinary CRTN excretion can be an expedient indirect method for evaluating body composition in healthy adult subjects. Data also suggest that the relationship between 3-MH and FFM is complex, limiting the possibility of predicting body composition from the excretion of this metabolite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Body Composition / physiology*
  • Body Water / physiology
  • Body Weight / physiology
  • Creatinine / urine*
  • Deuterium Oxide
  • Diet
  • Diet, Vegetarian
  • Female
  • Humans
  • Male
  • Methylhistidines / urine*
  • Residual Volume


  • Methylhistidines
  • Creatinine
  • Deuterium Oxide
  • 3-methylhistidine