Total body water estimated by measuring total-body electrical conductivity.

A second-generation total-body electrical conductivity (TOBEC) instrument for adults (HA-2) was evaluated against isotope dilution of 2H and 18O for its ability to estimate total body water (TBW) in 20 healthy adults. The highest correlation coefficient (0.997) and the lowest standard error of the estimate (0.68 kg) were obtained using the first (FC0) and third (FC2) Fourier coefficients of the transformed TOBEC signals and the variables height (m) times average lean circumference (m) and age (y) in the prediction equation of TBW as follows: TBW (H218O) in kg = 10.8 + (0.0724.FC0) - (0.221.FC2) + (0.0398.age) + (9.2.height.average lean circumference) where average lean circumference is the average of the lean chest, abdomen, and thigh circumferences. The TOBEC instrument for adults provides a suitable alternative for the estimation of TBW.