title: Accuracy of Siri and Brozek equations in the percent body fat estimation in older adults.
abstract: OBJECTIVE
  To identify which equation, Siri or Brozek, based on the two compartment model, provides a more accurate conversion of body density (BD) in percent body fat (%BF) in a group of older adults.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto.
  
  
  METHODS
  60 older adults, aged 60-92 years.
  
  
  METHODS
  Skinfold thickness was used to estimate BD through Visser et al. prediction equation. The conversion of BD to %BF was done with Siri (%BF-Siri) and Brozek (%BF-Brozek) formulas and these determined values were both compared to Dual-Energy X-ray Absorptiometry (%BF-DXA) evaluations.
  
  
  RESULTS
  A strong correlation between the %BF-DXA value and %BF-Siri (r=0.91, p < 0.001) and %BF-Brozek (r=0.91, p < 0.001) was found, although %BF-Siri and %BF-Brozek overestimated %BF-DXA (p < 0.001). The comparison of the %BF-Siri and %BF-Brozek mean values also revealed significant differences (p < 0.001). The %BF-Brozek reflects a better agreement than the %BF-Siri with %BF-DXA with respectively a mean difference of -4.0 %BF (limits of agreement = -10.9 to 2.9%) and -5.7 %BF (-12.6 to 1.2). The Bland and Altman plots confirmed that %BF-Brozek reflects a better agreement with %BF-DXA.
  
  
  CONCLUSIONS
  The results of the present study show that the use of Brozek equation may correspond to a more accurate alternative than Siri equation for the conversion of BD in %BF in older adults.
authors.affiliation: UISPA-IDMEC, Faculty of Engineering, University of Porto, Porto Portugal.
authors.forename: R S
authors.initials: RS
authors.lastname: Guerra
authors.forename: T F
authors.initials: TF
authors.lastname: Amaral
authors.forename: E
authors.initials: E
authors.lastname: Marques
authors.forename: J
authors.initials: J
authors.lastname: Mota
authors.forename: M T
authors.initials: MT
authors.lastname: Restivo
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D001837:Body Weights and Measures / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D006801:Humans; D008297:Male; D055641:Mathematical Concepts; D008875:Middle Aged; D015203:Reproducibility of Results; D012885:Skinfold Thickness