Evaluation of body composition by dual energy x-ray absorptiometry and two different software packages.

Dual energy x-ray absorptiometry (DXA) measures body composition, tissue distribution, bone mineral content (BMC), and bone mineral density (BMD). Differences are possible due to software versions. This investigation examined body composition, tissue distribution, BMC, and BMD measurements using a DXA (Lunar Corp., Madison, WI) with different software packages (versions 3.4 and 3.6R). Fifteen women, ages 20-40 yr, enrolled in a weight-loss study (body mass index = 28) and volunteered for body composition assessment by densitometry. BMC, BMD, and tissue distribution measurements were made using DXA. Results were analyzed once each with software versions 3.4 and 3.6R. BMC + total soft tissue, measured using DXA, was comparable to measured body weight (3.4 = 76.3 kg; 3.6R = 76.5 kg; weight = 76.5 kg). Lower BMC and BMD (5.5% and 1.8%, P < 0.01) were observed with 3.6R. Arm tissue mass was lower (1,530 g; P < 0.01) and fat declined (1,069 g; P < 0.01) with 3.6R. Leg tissue mass decreased 487 g (P < 0.01), but fat tissue increased (526 g, P < 0.01) with 3.6R. A larger fat mass (1,492 g) and lower lean mass (1,115 g) were observed with 3.6R compared with 3.4. Percent fat values by densitometry using DXA 3.4 and 3.6R were 38.1%, 39.9, and 41.9%, respectively. These results demonstrated differences in total body composition, lean and fat tissue distribution, and bone measurements from DXA software versions.