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Improved prediction formula for total body water assessment in obese women
A De Lorenzo1, G F Sasso, A Andreoli
1Department of Human Physiology, University Tor Vergata, Rome, Italy.
Objective:
To validate an improved formula for the calculation of total body water (TBW) from impedance values in obese women.
Subjects:
A sample of 37 overweight females BMI ranging from 29.5 to 44.1 kg/m2.
Measurements:
The reference measurements for TBW were obtained by deuterium oxide dilution. Body height (h), hip circumference (C) as well as body impedance at 100 kHz (Z100) were also measured.
Results:
The values obtained for h, C and Z100 were introduced in the calculations and the following developed formula for total body water was determined: TBW = 0.069 [hC2/(4 pi .Z100)]+19.671. The validity of this formula was assessed through the statistical test of Bland and Altman which we also performed for other formulas containing the weight and/or the height.
Conclusion:
We found that the accuracy of the prediction of TBW by our formula, although lower than those formulas using body weight, is higher than that which takes into account only body height. We conclude that body volume, expressed through body height and hip circumference, is a good choice of parameter in bioelectrical impedance measurements. The new approach can be useful in clinical settings for repeated monitoring of obese women, during diet-restricted treatment.