title: Assessment of research-based body composition techniques in healthy elderly men and women using the 4-compartment model as a criterion method.
abstract: OBJECTIVE
  To examine the accuracy, precision and bias of body fat estimates using traditional research based techniques, relative to those derived from a 4-compartment model in healthy, older men and women.
  
  
  METHODS
  Cross-sectional comparison of various body composition techniques in 41 healthy women (68.2 +/- 6.6 y) and 41 healthy men (70.2 +/- 7.0 y) with an age range of 57-90 y.
  
  
  METHODS
  Fat mass (FM) by the 4-compartment (4C) model was compared to that derived by dual energy X-ray absorptiometry (DXA), underwater weight (UWW) and total body water (TBW).
  
  
  RESULTS
  On a group mean basis, FM by the 4C model (24.4 +/- 7.4 kg in women, 18.2 +/- 7.6 kg in men) was similar to other techniques. The regression between FM by 4C and DXA significantly deviated from the line of identity (FM by 4C = 0.76*FM by DXA + 5.9 kg for women; 0.81*FM by DXA + 3.4 kg for men). FM by UWW was similar to FM by 4C model in men but not women (FM by 4C = 0.87*FM by UWW + 4.3 kg). FM by TBW was similar to FM by 4C model in women, but not men (FM by 4C = 0.80*FM by TBW + 4.7 kg). For DXA, there was no significant bias in estimates of FM in men or women. For UWW, there was significant bias in men with an over-estimate of FM among leaner subjects and under-estimates in fatter subjects. For TBW data, there was a significant bias in men with an under-estimate of FM among leaner subjects and over-estimate in fatter subjects.
  
  
  CONCLUSIONS
  Individual estimates of FM by DXA can be improved by correction factors that calibrate experimental data to standards such as the 4-C model. The assumptions of the Siri 2 compartment model are appropriate in healthy elderly men but not women, where a new equation is suggested. Inaccuracies in FM from TBW data are likely to be explained by age-related changes in the hydration of fat free mass (FFM).
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, 35294, USA.
authors.forename: M I
authors.initials: MI
authors.lastname: Goran
authors.forename: M J
authors.initials: MJ
authors.lastname: Toth
authors.forename: E T
authors.initials: ET
authors.lastname: Poehlman
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012106:Research