Body composition assessment: dual-energy X-ray absorptiometry (DEXA) compared to reference methods.

The use of dual energy X-ray absorptiometry (DEXA) for the assessment of body composition was examined in 55 adults (26 male & 29 female) ranging in age from 19 to 65 years. DEXA measures of bone mineral content (BMC, g), bone mineral density (BMD, g/cm2) and soft tissue (ST) were based on differential energy attenuation at dual energy levels of 40 and 70 keV. The ratio of the low- to high-energy attenuation in ST was used to quantify fat (%FatDEXA) and fat-free mass minus the bone component (FFMDEXA). BMC and BMD were significantly correlated (r = 0.82 and 0.60) with densitometric fat-free mass (FFMD). No significant differences were observed between the sum of FFMDEXA + BMC versus FFMD for either the males or females (males: FFMDEXA + BMC = 61.7 kg; FFMD = 59.1 kg; females: FFMDEXA + BMC = 43.8 kg; FFMD = 42.8 kg). Percentage body fat from DEXA for the women was equivalent to percentage fat from density (%FatDEXA = 30.8 versus %FatD = 32.2); however, significant differences were observed for the men (%FatDEXA = 19.4 versus %FatD = 23.5). Percentage fat differences for the men may be due to classification of individual soft tissue pixels. DEXA is reliable, easy to use, and appears to give accurate values for the estimation of FFM for both men and women. Additional research is needed to ascertain the cause of the differences in the estimation of percent body fat for men.