Scientific Validation of BIA

M.W. Valliant, D.K. Tidwell

The assessment of body composition (BC), specifically fat mass and fat-free mass is an important component of establishing nutritional status. Bioelectrical impedance (BIA) is a commonly used, non-invasive, low cost method to measure BC. African American (AA) females have a high rate of obesity so knowledge of BC is important to professionals working with this population. The objective of this study was to compare BIA (hand to foot model) to dual-energy X-ray absorptiometry (DXA) as the reference. BC was assessed by BIA (BIA 101 RJL System) and DXA (Hologic Delphi-W) in 100 healthy, AA females 18 – 40 years old with various body mass indices (range 17 – 47 kg/m2; mean = 29.53 +/- 6.86 s.d.). Both measures were completed in the morning following an overnight fast, physical inactivity for the previous 24 hours and in the supine position. Pearson.s correlation coefficient 0.94 (p = .01) indicated a strong correlation between the two methods and no significant statistical difference between the means (p = .72). Bland and Altman analysis showed strong agreement between the two methods across the range of body fat percentages indicating that they are comparable methods for measuring body fat percentage at lower and higher percentages of body fat. In conclusion, BIA is a suitable method to assess BC in adult AA females when factors such as food and beverage intake and physical activity are controlled.