The use of multifrequency impedance to determine total body water and extracellular water in obese and lean female individuals

OBJECTIVE: To validate the assessment of total body water (TBW) and extracellular water (ECW) by multi-frequency bioelectrical impedance. SUBJECTS: Twenty-five overweight but otherwise healthy subjects and 20 lean subjects. DESIGN: Cross-sectional. MEASUREMENTS: TBW and ECW were determined by dilution techniques. Prediction equations from the literature were used to calculate TBW and ECW from measured impedance at 100 and 50 kHz or 1 and 5 kHz, respectively. In 18 of the obese subjects, impedance was also measured with the electrodes placed at proximal sites. RESULTS: In lean and obese subjects, significant correlations were observed between the impedance index (H2/Z) at high frequencies with TBW (r=0.90, P