Body water distribution in severe obesity and its assessment from eight-polar bioelectrical impedance analysis

Abstract

Objective: To measure body water distribution and to evaluate the accuracy of eight-polar bioelectrical impedance analysis (BIA) for the assessment of total body water (TBW) and extracellular water (ECW) in severe obesity. Design: Cross-sectional study. Setting: Obesity clinic. Subjects: In all, 75 women aged 18-66 y, 25 with body mass index (BMI) between 19.1 and 29.9 kg/m 2 (ie not obese), 25 with BMI between 30.0 and 39.9 kg/m 2 (ie class I and II obese), and 25 with BMI between 40.0 and 48.2 kg/m 2 (ie class III obese). Methods: TBW and ECW were measured by 2 H 2 O and Br dilution. Body resistance (R) was obtained by summing the resistances of arms, trunk and legs as measured by eight-polar BIA (InBody 3.0, Biospace, Seoul, Korea). The resistance index at a frequency of x kHz (RI x ) was calculated as height 2 /R x . Results: ECW : TBW was similar in women with class III (4673%, mean7s.d.) and class I-II obesity (4573%) but higher than in nonobese women (3973%, Po0.05). In a random subsample of 37 subjects, RI 500 explained 82% of TBW variance (Po0.0001) and cross-validation of the obtained algorithm in the remaining 38 subjects gave a percent root mean square error (RMSE%) of 5% and a pure error (PE) of 2.1 l. In the same subjects, RI 5 explained 87% of ECW variance (Po0.0001) and cross-validation of the obtained algorithm gave a RMSE% of 8% and a PE of 1.4 l. The contribution of weight and BMI to the prediction of TBW and ECW was nil or negligible on practical grounds. Conclusions: ECW : TBW is similar in women with class I-II and class III obesity up to BMI values of 48.2 kg/m 2 . Eight-polar BIA offers accurate estimates of TBW and ECW in women with a wide range of BMI (19.1-48.2 kg/m 2 ) without the need of population-specific formulae. Sponsorship: Progetti di Ricerca Corrente, Istituto Auxologico Italiano.

Birth size, adult body composition and muscle strength in later life

“…The eight-polar BIA has been shown to give accurate estimates of body components in different populations without the need for population-specific algorithms. [28][29][30] This method is practical in large epidemiological studies with limited time for examination of each subject. 28,29 The outputs of InBody 3.0 are based on segmental 28,29 Resistance of arms, trunk and legs was measured at frequencies of 5, 50, 250 and 500 kHz with the subject standing barefoot in light clothing on the four foot electrodes on the platform of the analyzer and gripping the two palm and thumb electrodes.…”

“…A detailed description of the sequence of measurements has been described. [28][29][30] Isometric grip strength of the dominating hand was tested by a Newtest Grip Force dynamometer (Newtest Oy, Oulu, Finland). The maximum value of three squeezes was used in analyses.…”

Validation of bioelectrical impedance analysis for total body water assessment against the deuterium dilution technique in Asian children

“…The lower accuracy of BIA in the obese might be explained by the body water distribution changing with the increase of body fat. The obese have a higher relative amount of extracelluar water than lean individuals (Wang and Pierson Jr, 1976;Sartorio et al, 2005;Ritz et al, 2008). BIA impedance will therefore be lower in the obese at a given FFM and body weight and the general BIA equation will overestimate the TBW and FFM (Deurenberg et al, 1991).…”

Accuracy of eight-polar bioelectrical impedance analysis for the assessment of total and appendicular body composition in peritoneal dialysis patients

“…We have shown that eight-polar BIA offers accurate estimates of total body water, extracellular water, FFM and appendicular LTM in healthy and obese subjects (Bedogni et al, 2002;Malavolti et al, 2003;Sartorio et al, 2005).…”