Comparison of bioelectric impedance and near-infrared interactance for body composition assessment in a population of self-perceived overweight adults.

This study was conducted to determine the reliability and validity of bioelectric impedance (BIA) and near-infrared interactance (NIR) for body composition assessment in a population that considered themselves to be overweight, using hydrostatic weighing (HW) as the criterion method. Skinfold measurements were also taken for comparison, and the Jackson and Pollock (J-P) and Durnin and Womersley (D-W) equations were used to determine relative body fat. One hundred men and women, ages 18-61, with 15.5-43.3% body fat participated in the study. Reliability correlations for relative body fat (n = 19) were high for the skinfold equations (r = 0.99) and BIA (r = 0.95) and lower for NIR (r = 0.88). Analysis of variance showed that BIA, NIR, and J-P all significantly underestimated relative body fat in this population, while D-W significantly overestimated relative body fat. BIA, relative to HW, had correlations of r = 0.80-0.86 and SEEs of 3.4-3.6% body fat, while correlations for NIR were lower (r = 0.66-0.77) and SEEs were higher (3.8-4.3%) than for BIA. Correlations between D-W and HW ranged from r = 0.72 to 0.84 (SEE = 3.4-4.1%), while similar results were found for the J-P equations (r = 0.72 to 0.86, SEE = 3.0-4.1). BIA predicted 72% of the subjects within 4% of HW values while NIR, D-W, and J-P predicted only 61, 59 and 58%, respectively, within this same range.(ABSTRACT TRUNCATED AT 250 WORDS)