title: Accuracy of quantitative magnetic resonance and eight-electrode bioelectrical impedance analysis in normal weight and obese women.
abstract: OBJECTIVE
  Quantitative magnetic resonance (QMR) has previously been shown to both overestimate and underestimate average fat mass (FM) in humans. Eight-electrode bioelectrical impedance analysis (BIA) has previously been found biased as well as successfully validated. We report cross-sectional accuracy of QMR and eight-electrode BIA evaluated with air displacement plethysmography (ADP) as reference method.
  
  
  METHODS
  Fat mass and fat free mass (FFM) by QMR and eight-electrode BIA were evaluated against ADP as reference in 38 normal weight and 30 obese women. Total body water estimates by QMR and eight-electrode BIA were compared.
  
  
  RESULTS
  Fat mass was overestimated by QMR (1 ± 2 kg, p < 0.001) and was underestimated by eight-electrode BIA (1 ± 3 kg, p = 0.03, Bonferroni adjusted p = 0.29) in normal weight women. Fat mass was underestimated by both QMR (2 ± 2 kg, p < 0.001) and eight-electrode BIA (9 ± 3 kg, p < 0.001) in obese women. Fat free mass biases were of similar magnitude but in opposite direction to FM biases. Total body water estimates were larger by eight-electrode BIA compared to QMR (1-10 kg).
  
  
  CONCLUSIONS
  Fat mass and FFM by QMR were both biased but in opposite directions in both normal weight and obese women. Eight-electrode BIA FM and FFM estimates were imprecise and biased in obese women. Thus, QMR is more precise and more accurate than eight-electrode BIA for estimating body composition in women, but is not accurate enough to be used for individual single assessment of body composition.
authors.affiliation: Department of Physiology, Institution of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, Box 432, 405 30 Göteborg, Sweden. Electronic address: marja.bosaeus@neuro.gu.se.
authors.forename: Marja
authors.initials: M
authors.lastname: Bosaeus
authors.affiliation: Department of Physiology, Institution of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, Box 432, 405 30 Göteborg, Sweden.
authors.forename: Therese
authors.initials: T
authors.lastname: Karlsson
authors.affiliation: Department of Physiology, Institution of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Medicinaregatan 11, Box 432, 405 30 Göteborg, Sweden.
authors.forename: Agneta
authors.initials: A
authors.lastname: Holmäng
authors.affiliation: Department of Internal Medicine and Clinical Nutrition, Institution of Medicine, Sahlgrenska Academy at University of Gothenburg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Ellegård
mesh_terms: D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D004566:Electrodes; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis*; D010991:Plethysmography / Q000379:methods; D015203:Reproducibility of Results; D013548:Sweden; D055815:Young Adult
keywords: Air displacement plethysmography; Bioelectrical impedance analysis; Body composition; Obesity; Quantitative magnetic resonance