title: Comparison of methods for assessing body composition changes during weight loss.
abstract: OBJECTIVE
  Four cross-sectional studies have reported that percent body fat (%BF) measured by dual-energy x-ray absorptiometry (DXA) is significantly higher compared with values obtained with air displacement plethysmography (ADP) using the Bod Pod(R) in normal-weight individuals. This study was performed to confirm these findings in an overweight population and to assess whether DXA and ADP detected similar changes in body composition after moderate weight loss.
  
  
  METHODS
  Twelve women (42 +/- 8 yr) and 10 men (40 +/- 11 yr) had their %BF, fat mass (FM), and fat-free mass (FFM) measured using DXA and ADP before and after an 8-wk weight-loss program involving moderate energy restriction and exercise.
  
  
  RESULTS
  Body weight decreased significantly in women (-4.3 +/- 3.4 kg) and men (-4.7 +/- 3.1 kg). There were significant method (ADP vs DXA) and time (pre and post) effects but no method by time or gender interactions. Methods were significantly different in estimating %BF, FM, and FFM with ADP estimates of %BF and FM being lower and estimates of FFM higher than corresponding DXA values (P = 0.000). There were significant correlations accounting for a high degree of the shared variance between DXA and ADP (r = 0.98 to 0.99) for %BF, FM, and FFM and lower correlations for the changes in %BF (r = 0.66), FM (r = 0.86), and FFM (r = 0.34). In response to weight loss, the mean changes in %BF, FM, and FFM were not significantly different between methods (P > 0.05).
  
  
  CONCLUSIONS
  Both DXA and ADP measure changes in body composition after small to moderate weight loss to the same extent and with similar sensitivity.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Weyers
authors.forename: Scott A
authors.initials: SA
authors.lastname: Mazzetti
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Love
authors.forename: Ana L
authors.initials: AL
authors.lastname: Gómez
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D001823:Body Composition; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D012680:Sensitivity and Specificity