title: Assessing body composition with DXA and bioimpedance: effects of obesity, physical activity, and age.
abstract: OBJECTIVE
  This study evaluated to what extent dual-energy X-ray absorptiometry (DXA) and two types of bioimpedance analysis (BIA) yield similar results for body fat mass (FM) in men and women with different levels of obesity and physical activity (PA).
  
  
  METHODS
  The study population consisted of 37-81-year-old Finnish people (82 men and 86 women). FM% was estimated using DXA (GE Lunar Prodigy) and two BIA devices (InBody (720) and Tanita BC 418 MA). Subjects were divided into normal, overweight, and obese groups on the basis of clinical cutoff points of BMI, and into low PA (LPA) and high PA (HPA) groups. Agreement between the devices was calculated by using the Bland-Altman analysis.
  
  
  RESULTS
  Compared to DXA, both BIA devices provided on average 2-6% lower values for FM% in normal BMI men, in women in all BMI categories, and in both genders in both HPA and LPA groups. In obese men, the differences were smaller. The two BIA devices provided similar means for groups. Differences between the two BIA devices with increasing FM% were a result of the InBody (720) not including age in their algorithm for estimating body composition.
  
  
  CONCLUSIONS
  BIA methods provided systematically lower values for FM than DXA. However, the differences depend on gender and body weight status pointing out the importance of considering these when identifying people with excess FM.
authors.affiliation: Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Eszter
authors.initials: E
authors.lastname: Völgyi
authors.forename: Frances A
authors.initials: FA
authors.lastname: Tylavsky
authors.forename: Arja
authors.initials: A
authors.lastname: Lyytikäinen
authors.forename: Harri
authors.initials: H
authors.lastname: Suominen
authors.forename: Markku
authors.initials: M
authors.lastname: Alén
authors.forename: Sulin
authors.initials: S
authors.lastname: Cheng
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D000368:Aged; D000465:Algorithms; D001823:Body Composition; D050218:Body Fat Distribution; D017097:Electric Impedance; D015444:Exercise; D005260:Female; D005387:Finland; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*; D050177:Overweight / Q000503:physiopathology*; D015203:Reproducibility of Results; D012737:Sex Factors