Body fat and fat-free mass measured by bioelectric impedance spectroscopy and dual-energy X-ray absorptiometry in obese and non-obese adults

The aim of this study was to compare body fat mass (FM) and fatfree mass (FFM) estimates by 2 bioimpedance spectroscopy (BIS) with respective estimates by dual energy X-ray absorptiometry 3 (DXA) in obese and non-obese subjects. Body composition was measured in 93 obese and non-4 obese men and women by BIS device BodyScout (Fresenius Kabi) and DXA device Lunar iDXA 5 (GE Healthcare). Mean difference between the methods was analyzed by t-tests, and Bland-Altman 6 plots were generated for further examining differences between the methods. Mean difference 7 between the estimates by DXA and BIS (ΔDXA-BIS ) (Bland-Altman 95% limits of agreement) were 8 as follows: FM: 4∙1 (-2∙9 , 11∙2) kg, and 4∙5 (-2∙9 and 11∙8) %, FFM: -4∙1 (-11∙2 and 2∙9) kg, and -9 4∙5 (-11∙9 and 2∙9) %, indicating large inter-individual variation and statistically significant 10 underestimation of FM and overestimation of FFM by BIS as compared to DXA. The 11 underestimation of FMkg and overestimation of FFMkg were more pronounced in men than 12 women, and the underestimation of FM% and overestimation of FFM% were more pronounced in 13 normal weight (body mass index, BMI=20∙0-24∙9 kg/m2) than overweight and obese (BMI≥25∙0 14 kg/m2) subjects. BIS may be suitable for classification of a population into groups according to FM 15 and FFM. However, the large inter-individual variation suggests that this BIS device with the 16 proprietary software is in-sufficient for estimation of single individual body FM and FF