Total body water and lean body mass estimated by ethanol dilution.

Total body water (TBW) was determined on 35 subjects with a tritium (HTO) and an ethanol (ETH) dilution method, the latter using breath analyses for blood ethanol content. Lean body mass (LBM) was estimated by hydrostatic weighing. Mean values for water fraction (TBW/wt) were 0.618 +/- 0.05 with HTO and 0.603 +/- 0.06 with ETH. The difference was not significant. The correlation between the two methods was highly significant (r = 0.90, SEE = 3.5 liters, P less than 0.0001). High correlations were also found between TBW and LBM with either method for TBW (r = 0.94 with HTO, r = 0.91 with ETH). Mean values for TBW/LBM were 0.735 with HTO and 0.717 with ETH. The ETH method compares favorably with the HTO, it has the advantage that it is nonradioactive and can be repeated daily if necessary.