title: Prediction of whole-body and segmental body composition by bioelectrical impedance in morbidly obese subjects.
abstract: BACKGROUND
  Validated equations for body composition analysis using bioelectrical impedance (BIA) in morbidly obese (MO) subjects are scarce. Thus, our aim was todevelop new equations from physical and BIA parameters to estimate whole-body and segmental body composition inMO subjects, with dual-energy X-ray absorptiometry(DXA) as the reference method.
  
  
  METHODS
  A cross-sectional study on 159 Caucasian MO subjects (female 78%, age 43.5 ± 11.8 years, BMI 45.6 ± 4.9 kg/m2) divided in two groups was conducted: model building cohort (n = 110) and model validation cohort (n 0 49). Stepwise regression analysis was used to develop specific fat free mass (FFM) and fat mass (FM) equations.
  
  
  RESULTS
  Gender, body weight, and height2/impedance accounted, respectively, for 89.4% (p < 0.001) and 89.3% (p < 0.001) of the variability of DXA-total FFM in the two cohorts. Using the new equation, the mean difference between the DXA-FFM and BIA-FFM estimates was +0.180 kg (95% CI: -0.34 to +0.7 kg, p 0 NS), and the resulting limits of agreement were +6.76 and −6.40 kg. Similarly, good estimates of DXA truncal-, android-, and gynoid-FM from anthropometric and BIA parameters could be obtained from weight, height2/impedance, and waist and hip circumferences (respectively, R2 adjusted: 0.657, 0.776, and 0.770; p < 0.001).
  
  
  CONCLUSIONS
  The new equations derived from physical and BIA parameters provide accurate estimates of body composition in MO subjects.
authors.affiliation: Endocrinology and Nutrition Department, Hospital Clínic, IDIBAPS, University of Barcelona, Barcelona, Spain. ajimene1@clinic.ub.es
authors.forename: Amanda
authors.initials: A
authors.lastname: Jiménez
authors.forename: Wilberto
authors.initials: W
authors.lastname: Omaña
authors.forename: Lílliam
authors.initials: L
authors.lastname: Flores
authors.forename: María José
authors.initials: MJ
authors.lastname: Coves
authors.forename: Diego
authors.initials: D
authors.lastname: Bellido
authors.forename: Verónica
authors.initials: V
authors.lastname: Perea
authors.forename: Josep
authors.initials: J
authors.lastname: Vidal
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000465:Algorithms; D001823:Body Composition; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D009767:Obesity, Morbid / Q000453:epidemiology / Q000378:metabolism*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013030:Spain / Q000453:epidemiology; D018709:Statistics, Nonparametric