Abstract
This paper investigates the measurement of fat-free mass (FFM) by bioimpedance using foot-to-foot impedancemeters (FFI) with plantar electrodes measuring the foot-to-foot resistance R34 and hand-to-foot medical impedancemeters. FFM measurements were compared with corresponding data using Dual X-ray absorptiometry (DXA). Equations giving FFM were established using linear multiple regression on DXA data in a first group of 170 subjects. For validation, these equations were used on a second group of 86 subjects, and FFM were compared with DXA data; no significant difference was observed. The same protocol was repeated, but using electrodes on the right hand and foot in standing position to measure the hand to-foot resistance R13. Mean differences with DXA were higher for R13 than for R34. Effect of electrode size and feet position on resistance was also investigated. R34 decreased when electrode area increased or if feet were moved forward. It decreased if feet were moved backward. A proper configuration of contact electrodes can improve measurement accuracy and reproducibility of FFI.
Highlights
Overweight and obesity are recurrent problems in developed countries, especially with children, which may lead to various diseases such as diabetes, cancers, and cardiovascular disease [1]
In a study conducted in our laboratory with healthy volunteers using a Tefal BodyVision foot-tofoot impedancemeters (FFI), we found mean values of R34 of 467 ohms in males and 549 ohms in females, versus mean values of 500 ohms for R13 in men and 632 in women
Jebb et al [7] observed a slightly higher mean bias with Dual X-Ray absorptiometry (DXA) for a Tanita than with a Bodystat, but smaller standard deviation (SD) of differences. They noted that bioimpedance measurement overestimated fat mass (FM) in very lean subjects, while it underestimated it in obese subjects; they attributed this situation to the effect of FFM hydration
Summary
Overweight and obesity are recurrent problems in developed countries, especially with children, which may lead to various diseases such as diabetes, cancers, and cardiovascular disease [1]. It is important for this population to be able to monitor the development of their fat mass (FM) in order to adapt their food intake and exercise. Bioimpedance is a simple technique for measuring body composition, including fatfree-mass (FFM) which combines LBM and BMC. FFM is calculated using an empirical equation determined by comparison with DXA data and containing weight (W), height (H), subject age, and the body resistance (R), or the impedance (Z). FM is calculated as the difference between W and FFM
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