title: Body composition in underweight elderly subjects: reliability of bioelectrical impedance analysis.
abstract: OBJECTIVE
  In underweight elderly subjects it is important to estimate body composition and particularly fat-free mass (FFM). Bioelectrical impedance analysis (BIA) is a non-invasive method in determining FFM, but its usefulness in these frail subjects should be verified. The aim of this study is to verify in underweight elderly people the reliability of previously published BIA formulas in detecting FFM.
  
  
  METHODS
  Fifty-seven hospitalized elderly subjects (27 males and 30 females) with body mass index <20 kg/m(2) were selected. In all subjects, FFM was detected by dual energy X-ray absorptiometry. Moreover, BIA measurements were performed at standard frequency (50 kHz and 800 microA) and FFM was derived using the main previous published BIA equations.
  
  
  RESULTS
  In men, Kyle and Rising equations gave acceptable estimates of FFM with a mean error, respectively, of 1+/-1.9 and 1.4+/-1.7 kg. Also RJL formula could be used after adjusting for a correction factor. In women, no equation seemed sufficiently reliable to estimate FFM.
  
  
  CONCLUSIONS
  BIA method seems useful to evaluate body composition in underweight elderly men but it seems to have intrinsic limits in women. Nevertheless, the variability in behavior of the different equations suggests to be careful in adopting BIA equations.
authors.affiliation: Department of Medical and Surgical Sciences, Division of Geriatrics, University of Padua, Padova, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Lupoli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sergi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Coin
authors.forename: Egle
authors.initials: E
authors.lastname: Perissinotto
authors.forename: Stefania
authors.initials: S
authors.lastname: Volpato
authors.forename: Luca
authors.initials: L
authors.lastname: Busetto
authors.forename: E M Emine Meral
authors.initials: EM
authors.lastname: Inelmen
authors.forename: Giuliano
authors.initials: G
authors.lastname: Enzi
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D044342:Malnutrition; D008433:Mathematics; D018482:Muscle, Skeletal / Q000502:physiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity