title: Impact of bone mineral estimates on percent fat estimates from a four-component model.
abstract: OBJECTIVE
  The primary purpose of this study was to determine the impact of bone mineral content (BMC) from QDR 1000/W and DPX-L dual-energy x-ray absorptiometers (DXA(QDR) and DXA(DPX-L) on percent fat (%fat) estimates from a four-component model. A secondary purpose was to test the accuracy of %fat estimates from DXA(QDR) and DXA(DPX-L) using %fat estimates from a four-component model as the criterion.
  
  
  METHODS
  Percent fat, fat mass, and fat-free mass (FFM) were determined from DXA(QDR) and DXA(DPX-L) and from a four-component model based on measures of body density from underwater weighing, body water from deuterium dilution, and BMC from DXA(QDR) (4C(QDR)) or DXA(DPX-L) (4C(DPX-L)) in young men (N = 14) and women (N = 10).
  
  
  RESULTS
  BMC was significantly lower using DXA(QDR) compared with DXA(DPX-L) (approximately 11%), resulting in slightly lower estimates of %fat and fat mass and slightly higher estimates of FFM from 4C(QDR) than 4C(DPX-L). Although estimates of %fat, fat mass, and FFM from DXA(QDR) and DXA(DPX-L) were not different than those from a four-component model, there was considerable individual variability between methods. Furthermore, %fat from DXA(QDR) was lower than %fat from 4C(DPX-L).
  
  
  CONCLUSIONS
  We conclude that using BMC from different DXA instruments has a minimal impact on %fat, fat mass, and FFM estimates from a four-component model. The large variability in %fat estimates between the two DXA instruments and those from a four-component model does not support DXA as a criterion method of body composition. Further studies involving larger sample sizes and specific population groups are needed to assess the validity of body composition measurements from DXA.
authors.affiliation: Department of Foods and Nutrition, The University of Georgia, Athens 30602-3622, USA. cmodlesky@fcs.uga.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Modlesky
authors.forename: E M
authors.initials: EM
authors.lastname: Evans
authors.forename: M L
authors.initials: ML
authors.lastname: Millard-Stafford
authors.forename: M A
authors.initials: MA
authors.lastname: Collins
authors.forename: R D
authors.initials: RD
authors.lastname: Lewis
authors.forename: K J
authors.initials: KJ
authors.lastname: Cureton
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D001823:Body Composition; D001834:Body Water; D015519:Bone Density; D005260:Female; D006801:Humans; D008297:Male; D008722:Methods; D008962:Models, Theoretical