Assessment of human body composition using dual-energy x-ray absorptiometry and bioelectrical impedance analysis

Human body composition, particularly the content of fat tissue and its distribution, has been extensively measured in healthy, diseased, obese and elderly subjects. A variety of non-invasive methods have been applied for these studies. Bioelectrical impedance analysis (BIA) is a commonly used method, based on the conduction of electrical current in the body and the differences in the ability to conduct electricity between the fat and water components of the body. Recently, dual-energy x-ray absorptiometry (DEXA) has been introduced for bone mass, bone mineral density and body composition studies. Unlike other methods, DEXA measures three components of the body: bone mineral content, fat tissue mass, and lean tissue mass, and additionally regional fat distribution. The objective of this study was to compare body composition as assessed by DEXA and BIA methods in a sample of 100 patients.

Body composition was studied in 100 consecutive subjects, 59 women and 41 men. The lean body mass (LBM), fat body mass (FBM), and percent body fat (%BF) were measured by the DEXA and BIA techniques.

There were highly statistically significant linear relationships between LBM, FBM and %BF assessed by DEXA and BIA in both sexes (p<0.001 for all measurements). No influence of age or BMI on the relationship between DEXA and BIA results was observed. Differences were observed between DEXA and BIA measurements of both fat and fat-free tissue. The results suggest that DEXA may underestimate the LBM and overestimate body fat compared with BIA, probably due to different assumptions about the constants.

We conclude that both methods are suitable for body composition studies.