Effect of gender, body composition, and equilibration time on the 2H-to- 18O dilution space ratio

M. I. Goran, E. T. Poehlman, K. S. Nair, E. Danforth

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17 Scopus citations


Physiological sources of variation in the 2H-to-18O dilution space ratio (DSR) were examined in 34 males and 20 females (4-78 yr; 14.7-143.2 kg; 1.8-61.0% body fat). Dilution spaces were obtained by time 0 extrapolation of isotope washout over 10-14 days, and body composition was obtained by underwater weight (adults) or bioelectrical impedance (children). The mean DSR was 1.050 ± 0.015 (range 1.029-1.111), significantly higher (P < 0.001) than the traditionally assumed value of 1.029 based on exchange over 4 h. Use of the value 1.029 causes a systematic 8% overestimate of energy expenditure from doubly labeled water, relative to use of the value 1.05. The DSR was not related to body composition or age but was significantly higher (P < 0.05) in males (1.052 ± 0.016) than in females (1.044 ± 0.012). This gender effect was not explained by differences in the number of exchangeable hydrogens in the body. We conclude 1) variation in the 2H-to-18O DSR is not explained by body composition but is influenced by the chemical availability of exchangeable hydrogens to undergo exchange; 2) because the DSR is not easily predicted, use of the observed dilution spaces are recommended; 3) if a fixed DSR is used, values of 1.044 and 1.052 are recommended in females and males, respectively.

Original languageEnglish (US)
Pages (from-to)E1119-E1124
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number6 26-6
StatePublished - 1992


  • adiposity
  • age
  • doubly labeled water
  • isotope exchange
  • total body water

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)


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