Preliminary evidence that DEXA provides an accurate assessment of body composition

Abstract

Kohrt, Wendy M. Preliminary evidence that DEXA provides an accurate assessment of body composition. J. Appl. Physiol. 84(1): 372–377, 1998.—It was previously found that dual-energy X-ray absorptiometry (DEXA) underestimated central body fat. The purposes of this study were to determine whether an updated version (enhanced version 5.64) of the analysis program corrected this problem ( experiment 1) and to compare body composition assessed by DEXA and hydrodensitometry (HD) in women ( n= 225) and men ( n = 110) across a 21- to 81-yr age range ( experiment 2). For experiment 1, 10 subjects underwent DEXA procedures in a control condition and with packets of lard positioned over either the thighs or the truncal region. DEXA accurately quantified the additional mass as ∼96% fat, regardless of position. For experiment 2, DEXA yielded higher ( P < 0.001) estimates of fatness than did HD (32.1 ± 12.0 vs. 31.2 ± 10.1%). The mean difference between the two methods was similar in young, middle-aged, and older subjects, but was different in men (HD − DEXA, 1.6 ± 3.4% of body wt) than in women (−2.1 ± 3.8% of body wt). Correcting the density of fat-free mass for variance in the bone mineral fraction of fat-free mass reduced the difference between the methods in men from 1.6 ± 3.4 to −0.7 ± 2.9% but widened it in women from −2.1 ± 3.8 to −3.5 ± 3.4%. A second correction procedure that adjusted for variance in water, protein, and mineral fractions of fat-free mass eliminated the differences in estimates of fat content by DEXA and HD in both men (21.1 ± 9.3 vs. 20.6 ± 8.4%, respectively) and women (37.5 ± 9.3 vs. 36.8 ± 8.0%, respectively). These results provide encouraging, but not definitive, evidence that the assessment of body composition by DEXA is accurate under the specified conditions.