Author
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Lukaski, Henry |
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Siders, William |
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Submitted to: Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/18/2003 Publication Date: 10/1/2003 Citation: Lukaski, H.C., Siders, W.A. 2003. Validity and accuracy of regional bioelectrical impedance devices to determine whole-body fatness. Nutrition. 19:851-857. Interpretive Summary: Overweight and obesity are growing at alarming rates world-wide. Traditionally, assessment of human body composition, particularly body fatness, has relied on either very sophisticated methods only found in a research laboratory or indirect indicators based on body weight and height. Recently, an adaptation of the bioelectrical impedance method has been made available to the public for at home assessment of body fatness. This technique introduces a safe, low level, radio frequency alternating electrical current into the body and measures how the current is conducted. Commercial devices either introduce the electrical current at the hands with contact electrodes in hand grips or the feet with electrodes on pads that contact the soles of the feet. We determined the reproducibility and accuracy of these devices to measure body fatness in comparison to a reference method, dual x-ray absorptiometry, in 110 healthy adults. We found that the devices yield body fatness values that are quite variable (±5%) and significantly less than true values. Furthermore, because these devices require an individual to enter personal information including age, sex, eight, and height, we tested if this information is as good or better than the combination of the information and measured impedance. For the adults studied, predictions of body fatness with the physical characteristic information gave body fat values similar to the reference method. Thus, the currently available devices are not recommended for general use in measuring body composition. This information will be useful to public health officials and dieticians who work with people seeking to monitor their body composition either to assess obesity or determine progress in weight reduction programs. Technical Abstract: The growing emphasis on obesity as a risk factor for chronic disease, and the commercial availability of impedance devices for the at-home assessment of body fatness (% fat), have stimulated the need for a critical evaluation of the validity of these instruments. We determined the reproducibility and accuracy of two commercial impedance devices that use either upper body (hand-to-hand) or lower body (foot-to-foot) contact electrode placements by comparison with dual x-ray absorptiometry (DXA) measurements of body fatness in 62 women and 48 men aged 21-60 yr. Variability in body mass (1%), measured in 10 adults on five consecutive days, was less than body fatness predicted with the upper (2 to 20%) and lower (3 to 5%) body devices. Using a 50 kHz, tetrapolar bioelectrical impedance plethysmograph with surface electrode placements on the upper and lower limbs, regional and whole body impedance values were correlated (P<0.0001). Regional and whole body impedance values were different (P<0.05) in the women, whereas upper and lower body values were lower (P<0.05) than whole body impedance in the men. DXA determinations of body fatness were similar to predictions based on models derived from physical characteristics but significantly different (P<0.05) than estimates from the impedance devices, which underestimated body fatness in women. Bias in predictions of body fatness with the regional devices was systematically (P<0.0001) related to body fatness, underestimating with increasing levels of fatness. Use of regional impedance devices to assess body fatness is limited by a lack of precision and accuracy. |
