Estimation of total body composition by regional dual photon absorptiometry

The accuracy of estimating total body composition from dual photon absorptiometry (DPA) and the soft tissue attenuation ratio (Rst) from regional scans over the abdomen was investigated in a group (n = 82) of young adult (age = 17-38 years) females with diverse activity histories. Forearm bone mineral content (BMC) was estimated from single photon absorptiometry. Lumbar vertebrae and femur BMC, and trunk (lumbar region) soft tissue composition (Rst) were estimated from DPA. Percent body fat, the criterion variable, was estimated from body density (BD) after adjusting for individual variation in BMC, an important source of variability in body density. The test-retest reliability of Rst, assessed in a second group of subjects (n = 30), was excellent (r = 0.99; SE_M = 0.10%). Rst was significantly (P ≤ .05) correlated with body density (r = .78), limb and especially trunk skinfolds, and predicted total body fat (%) with an SEE of 3.9%. These results demonstrate that DPA is a useful technique for obtaining estimates of both bone mineral and soft tissue composition, particularly in populations suspected to have significant bone loss. Given the association between Rst and trunk (abdominal) fat, DPA may prove to be a useful technique for investigating the association between abdominal fat and disease.