Abstract
Bioelectrical impedance (BI) is commonly used to estimate body composition in different populations. The aim of this study was to determine the accuracy of bipolar BI (Omron BF 300) in estimating relative body fat (%F) by comparing it with dual-energy X-ray absorptiometry (DEXA). %F was measured in 66 men (18 to 33 years) with a mean body weight of 73.7 ± 8.4 kg, height of 175.1 ± 6.5 cm, body mass index of 23.9 ± 2.2 kg/m2, %FBI 15.1 ± 4.4%, and %FDEXA 17.7 ± 5.1%. A paired t-test, correlation test, standard error of the estimate (SEE), and residue analysis were used to evaluate the accuracy of the method. BI significantly (p < 0.05) underestimated %F and, the correlation between the two methods was moderate (r = 0.769). Residue analysis showed the lack of agreement between the two methods, with an average error of -2.6 percentage points (95%CI: -9.1; 3.9). The SEE was above the recommended level (>3.5%F) in 42% of the sample. In subjects with higher fat accumulation (%F >20%), the Omron BF BI model produced greater bias in the %F measurement. Therefore, in the case of adult men, the Omron BF 300 BI model does not agree with the DEXA measurement for the estimation of %F in adult men. In addition, the higher the level of fat accumulation, the higher the error in estimated %F.
Highlights
The scientific community has shown great interest in the quantification of body composition, body fat[1,2]
Mean %F measured by Dual-energy X-ray absorptiometry (DXA) was 17.7%, indicating the presence of subjects with adequate %F and overweight and obese subjects[13,16]
These findings demonstrate the external validity of the study since the sample was heterogenous in terms of %F as observed in the general population, permitting generalization of the results
Summary
The scientific community has shown great interest in the quantification of body composition, body fat[1,2]. The fact that relative body fat (%F) is associated with non-transmissible chronic diseases has encouraged the search for an accurate estimation technique. BI is based on the concept that an electric current passes more through hydrated fat-free tissue and extracellular water than fat because of the higher electrolyte content of the former, reducing electric resistance or impedance[11]. Resistance to the electric current is inversely proportional to fat content. The traditional BI method is based on the estimation of electric resistance using four or eight electrodes (tetrapolar or octapolar BI, respectively) to transmit the electric current through the body. The resistance observed permits to estimate %F and other body composition components using regression equations. There are simpler devices containing only two electrodes (bipolar BI) coupled to the apparatus itself, which are based on the same principle as the other methods
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