[A comparison between double-photon absorptiometry (DEXA), impedance and anthropometry in the study of the body composition of obese subjects].

Dual-energy X ray absorptiometry (DEXA) is primarily used in the assessment of bone mineral. However, the transmissions of the two different energy beams in nonbone areas can be processed to calculate the amount of fat and free-fat mass of the soft tissues. We have compared the estimation of body fat mass (FM) by DEXA with data derived from anthropometric (A) (During & Womersley formula) and impedance (BIA) measurements. We have studied 10 subjects, 8 female and 2 male, age 39 +/- 17, weight 97.4 +/- 17.2 kg. The results were: FM 44.4 +/- 8.5 kg (DEXA), 40.6 +/- 6.3 kg (A) and 38.4 +/- 9.8 kg (BIA); FFM 52.1 +/- 14.1 kg (DEXA), 56.8 +/- 13.9 kg (A) and 58.8 +/- 13.6 kg (BIA). The correlation was higher between DEXA and A (r = 0.88, for women r = 0.94). BIA results change depending on the equation used to derive Lean Body Mass (LBM) according to different authors. DEXA measurements are independent from the explorer, whereas A and BIA determinations can change in separate occasions with the same or different observer. Therefore, DEXA method seems more reliable than BIA for the assessment of FM. If DEXA technology is not available, our results support the use of anthropometric over impedance measurements.