Relationships Between Dual‐Energy X‐Ray Absorptiometry Fat and Lean Tissue Masses and Standing and Sitting Bioimpedance Spectroscopy Variables in Healthy Men and Women

Abstract

Historically, for the assessment of fluid volumes, bioimpedance spectroscopy (BIS) measurements have been performed on the right side of the body, in a supine position, using gel‐backed wet electrodes. Most bioimpedance devices utilize a standing position and metal electrodes while utilizing multiple frequencies (typically < 30) and are not capable of measuring resistance at hundreds of frequencies needed for BIS calculations. BIS requires data collected over hundreds of frequencies to generate complex Cole models. From the Cole models resistances at a frequency of zero kHz (R0) and infinite kHz (Rinf) can be determined. R0 and Rinf allow for the calculation of extracellular and intracellular resistance and can be used to calculate fluid volumes without population‐based algorithms. The purpose of the study was to compare BIS measurements taken when subjects were standing and sitting using fixed metal electrodes and evaluate the relationships of raw and fluid volume data to dual‐energy X‐ray absorptiometry (DXA) data (lean soft tissue and fat tissue) in healthy men and women. Fifty‐five healthy men and women (m = 22, f = 33, 24 +/− 8 years, 169.5 +/− 10.5 cm, 72.3 +/− 14.9 kg) participated in the study. Whole body right side BIS measurements were taken in both a sitting and standing position with both methods utilizing metal electrodes (SOZO, ImpediMed, Inc.). Whole body DXA scans were performed using a Lunar Prodigy Primo (GE Healthcare). Raw BIS data included R0, Rinf, resistance at 50 kHz (R50), reactance at 50 kHz (Xc50), and phase angle at 50 kHz (Phase50). Calculated fluid volumes from BIS included intra‐cellular fluid (ICF), extra‐cellular fluid (ECF), and total body water (TBW). DXA variables included lean soft tissue (LST) and fat tissue (FT). All raw variables and fluid volumes from BIS were significantly related to DXA LST (p < 0.035) with fluid volumes having the highest correlation (r > 0.94) for both sitting and standing BIS measurements. All standing BIS variables had higher relationships to DXA LST compared to sitting BIS variables with an average improvement of r = 0.019 (0.009 to 0.032). Fat tissue from DXA was only significantly related to Xc50 (r = −0.315, p = 0.019) in the sitting position. In conclusion, measurements from BIS in a sitting or standing position with metal electrodes were shown to be highly related to DXA LST (highest r = 0.973). Due to the high correlation with TBW, ICF, and ECF to LST, a simple, single variable equation could be implemented using any one of the aforementioned variables to calculate LST or muscle using the current BIS method in healthy men and women. Future research should identify which of the above three variables is ideal for tracking changes in LST/muscle mass over time in both healthy and diseased populations.Support or Funding InformationSupport provided by ImpediMed, Inc. to Eastern Kentucky University. JRM is an employee and stockholder of ImpediMed, Inc.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.