The use of multi-frequency impedance to determine total body water and extracellular water in obese and lean female individuals (original) (raw)

1997, International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity

To validate the assessment of total body water (TBW) and extracellular water (ECW) by multi-frequency bioelectrical impedance. Twenty-five overweight but otherwise healthy subjects and 20 lean subjects. Cross-sectional. 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. In lean and obese subjects, significant correlations were observed between the impedance index (H2/Z) at high frequencies with TBW (r = 0.90, P < 0.001 in lean and r = 0.80, P < 0.001 in obese subjects) and at low frequencies with ECW (r = 0.87, P < 0.001 and r = 0.77, P < 0.001 respectively). Proximal placement of electrodes slightly improved the correlation between the impedance index and TBW (from r = 0.83 to r = 0.90 at 50 kHz and from r = 0.85 to r = 0....