A relationship between bioelectrical impedance and total body water in young adults.

Total body water was measured using the stable isotope H2(18)O in 14 young adults. Body resistance was assessed using a tetrapolar technique using a Holtain body-composition analyzer. Total body water was highly correlated (r = 0.96; p less than 0.001) with height2/resistance. The inclusion of body weight in the prediction equation reduced the standard error of estimate from 1.9 to 1.51. Bioelectrical resistance can be used to assess other body-composition parameters such as fat-free mass and fat mass, but this use involves a number of assumptions which may confound the relationship. We suggest that the measurement of bioelectrical impedance may, however, have a role in the estimation of total body water.