Total body water (TBW) can be estimated from a person's bioelectrical impedance, height and weight. Schoeller and Luke used these parameters to predict the total body water of Caucasians and Afro-Americans. The authors are from the University of Wisconsin in Madison and Loyola University in Maywood, Illinois.


The impedance index (height in centimeters, squared, divided by the resistance in ohms) is a significant predictor of total body water.



(1) Bioelectrical impedance analysis (BIA) was performed with a body composition analyzer (model BIA-101, RJL Systems, Detroit) with a right-sided tetrapolar placement of electrodes.

(2) The whole body resistance was recorded 3-5 times and the mean value calculated.


impedance index =

= ((height in centimeters)^2) / (resistance in ohms)


total body water for a Caucasian in kilograms =

= (0.499 * (impedance index)) + (0.080 * (body weight in kilograms)) + 2.9


total body water for an Afro-American in kilograms =

= (0.562 * (impedance index)) + (0.081 * (body weight in kilograms)) + 1.3


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