Abstract
Objective. To compare body composition assessment by bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) in a multiethnic sample of adolescent girls. Method. Data were from a physical activity intervention study among 254 14–20-year-old sedentary American girls, including 69 whites, 74 blacks, 42 Hispanics, and 69 Asians. Height and weight were objectively measured. Body composition was assessed using a foot-to-foot BIA and a fan-beam DXA. We calculated ethnic-specific estimates of percentage body fat (BF%), fat mass (FM), fat mass index (FMI), fat-free mass (FFM), and fat-free mass index (FFMI) from BIA and DXA. We used Bland-Altman plots to examine ethnic-specific agreement between BIA and DXA, and used linear regression to test whether the BIA-DXA difference varied across the mean. Results. Compared to DXA, BIA estimates of fat measures (BF%, FM, and FMI) were lower and lean tissue measures (FFM and FFMI) higher. For example, the BIA-estimated BF% was lower than the DXA estimate by between 4.9% (95% CI: −5.9, −3.9) in blacks and 8.7% (−7.0, −5.0) in Asians, with large limits of agreement (−15.4 to −5.4 in blacks and −16.8 to −0.4 in Asians). Regression analysis showed that BIA-DXA differences were not constant across means for any body composition measure among Asians or for any measure except BF% among whites. Conclusion. Compared to DXA, BIA yielded lower estimates of adiposity in a multiethnic adolescent sample. BIA-DXA differences varied by ethnicity, and across mean body composition values for some ethnicities.
Acknowledgements
This study was supported by grants R01 DK063107 (D. Neumark-Sztainer, principal investigator) from the National Institute of Diabetes and Digestive and Kidney Diseases, and T32-HL07779 (A. Folsom, principal investigator, supported K. Meyer) from the National Heart, Lung, and Blood Institute, and M01-RR00400 from the National Center for Research Resources, National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Diabetes and Kidney Diseases, the National Heart, Lung, and Blood Institute, the National Center for Research Resources, or the National Institutes of Health.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.