title: Ethnic variation in body composition assessment in a sample of adolescent girls.
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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN 55454, USA. meyer088@epi.umn.edu
authors.forename: Katie A
authors.initials: KA
authors.lastname: Meyer
authors.forename: Sarah
authors.initials: S
authors.lastname: Friend
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hannan
authors.forename: John H
authors.initials: JH
authors.lastname: Himes
authors.forename: Ellen W
authors.initials: EW
authors.lastname: Demerath
authors.forename: Dianne
authors.initials: D
authors.lastname: Neumark-Sztainer
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity; D000293:Adolescent; D000328:Adult; D044466:Asian People; D044383:Black People; D001823:Body Composition; D017097:Electric Impedance; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D044465:White People