Estimation of body fatness by air displacement plethysmography in African American and white children

The purpose of this study was to determine the ability of air displacement plethysmography (ADP) to estimate body fatness in prepubertal and early pub ertal African American and white children. One hundred nineteen nonoverweig ht and overweight boys (N=56) and girls (N=63), age (mean +/- SD) 9.8 +/-1. 7 y, body mass index 25.9 +/-7.6 kg/m(2) (range, 14.2-47.0 kg/m(2)), and me an percent body fat (%BF) by dual-energy x-ray absorptiometry (DXA) 39.2 +/ - 11.7% (range, 12.2-57.5%), were studied. %BF by ADP was compared with DXA %BF estimates and with body fat by several field methods: skinfold thickne sses using the Slaughter et al. equations (Hum Biol 60: 709-723, 1988), bio electrical impedance analysis (BIA) using the Houtkooper et al. equation (J Appl Physiol 72: 366-373, 1992), and a predictive equation using skinfold thicknesses, BIA, and weight (Goran et al.: Am J Clin Nutr 63: 299-305, 199 6). All methods used to estimate %BF were significantly correlated with DXA (all p<0.0001), with r(2) ranging from 0.85 (skinfold measurements) to 0.9 5 (ADP). ADP using the Siri equation underestimated %BF by -1.9% (p<0.001); the Bland-Altman limits of agreement (defined as +/-2 SD) were +/-7.4%. %B F by ADP-Siri underestimated %BF by DXA by 3.0% for girls (p<0.001) and by 0.6% for boys (NS). Agreement between body fat estimation by ADP and DXA di d not vary with age, race, or pubertal stage. Application of the age-adjust ed Lohman model to ADP significantly increased the magnitude of the underes timation to -6.9% (p<0.0001). Prediction of %BF by the Slaughter skinfold t hickness equation showed no significant mean bias for the overall data, but significantly underestimated %BF in girls (-3.7%) while overestimating %BF in boys (+2.4%) with wide limits of agreement (+/- 17.7%, p<0.01 versus AD P). %BF by the Houtkooper BIA equation or Goran model underestimated %BF to a significantly greater degree than ADP (Houtkooper, -8.1%; Goran, -10.1%; both p<0.0001 versus DXA or ADP). Determination of %BF from ADP using the Siri model slightly underestimates %BF as determined by DXA in girls, but a ppears to be superior to existing field methods both in accuracy and limits of agreement. Because of the ease with which it can be performed, ADP may prove useful for investigations of adiposity in children.