title: Multifrequency bioelectrical impedance analysis and bioimpedance spectroscopy for monitoring fluid and body cell mass changes after gastric bypass surgery.
abstract: OBJECTIVE
  There is a growing need for clinically applicable body composition assessment tools for extremely obese individuals. The objective of this research was to evaluate several bioimpedance techniques for monitoring changes in fluid, particularly intracellular water (reflecting body cell mass) after bariatric surgery.
  
  
  METHODS
  Fifteen extremely obese women (body mass index: 48.9+/-7.0 kg/m(2); age: 48+/-9 years) were assessed before (baseline; T1), and approximately 6 weeks after gastric bypass surgery (T2) by several multifrequency bioelectrical impedance analysis approaches (MFBIA; QuadScan 4000), a bioimpedance spectroscopy device (BIS; Hydra 4200), and multiple dilution.
  
  
  RESULTS
  BIS provided intracellular water estimates that were comparable to criterion, based on mean comparisons, at both time points (T1: criterion: 24.2+/-3.1L, BIS: 24.0+/-3.7 L; T2: criterion: 20.6+/-3.7 L, BIS: 19.7+/-3.2L). MFBIA (with Deurenberg equations) provided comparable measures to criterion only at T2 (criterion: 20.3+/-3.7L, MFBIA: 20.6+/-2.7 L). Both MFBIA (with QuadScan proprietary equations) and BIS produced estimates of intracellular water change that were comparable to dilution. There was substantial variability in individual volume measures.
  
  
  CONCLUSIONS
  Although MFBIA and BIS hold promise as convenient techniques for assessing fluid changes, individual variability in measurements makes them impractical for assessment of extremely obese patients in the clinical setting.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, MN 55108-6099, USA. dobra011@umn.edu
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Mager
authors.forename: Shalamar D
authors.initials: SD
authors.lastname: Sibley
authors.forename: Tiffany R
authors.initials: TR
authors.lastname: Beckman
authors.forename: Todd A
authors.initials: TA
authors.lastname: Kellogg
authors.forename: Carrie P
authors.initials: CP
authors.lastname: Earthman
mesh_terms: D001823:Body Composition / Q000502:physiology*; D001834:Body Water / Q000502:physiology*; D017097:Electric Impedance; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D009765:Obesity / Q000601:surgery*