title: Good agreement between bioelectrical impedance and dual-energy X-ray absorptiometry for estimating changes in body composition during weight loss in overweight young women.
abstract: OBJECTIVE
  To compare estimations of body composition using two different methods of bioelectrical impedance analysis (BIA) with dual X-ray absorptiometry (DXA) for estimating body composition during weight loss in overweight and obese young females.
  
  
  METHODS
  Twenty-four overweight or obese females (age 29.5+/-6.1 years, BMI 36.4+/-4.3 kg/m(2)) had body composition assessed using single-frequency (Tanita Ultimate Scale; SF-BIA) and multi-frequency (Impedimed SFB7; MF-BIA) BIA and DXA before and after a 10-week weight loss intervention.
  
  
  RESULTS
  MF-BIA estimates of body composition showed good absolute agreement with DXA, as evidenced by the small biases in the estimation of fat free mass (FFM), fat mass (FM) and percentage body fat (BF%); however, the limits of agreement for each variable were wide (bias +/-1.96 standard deviation; FFM -1.6+/-6.5 kg, FM 1.6+/-6.5 kg, BF% 1.4+/-6.3%). SF-BIA exhibited a larger bias with wide limits of agreement (FFM 3.8+/-9.1 kg, FM -3.8+/-9.1 kg, BF% -4.37+/-10.3%). During weight loss the values provided by MF-BIA and SF-BIA were not significantly different from DXA (p> or =0.89) due to small bias and the limits of agreement were narrow (MF-BIA: FFM -0.01+/-3.74 kg, FM 0.01+/-3.74 kg, BF% 0.22+/-3.40%; SF-BIA: FFM 0.40+/-3.92 kg, FM -0.40+/-3.92 kg, BF% 0.25+/-3.40%).
  
  
  CONCLUSIONS
  Compared with DXA, both the MF-BIA and SF-BIA accurately assessed changes in body composition with weight loss but, compared with SF-BIA, MF-BIA provided superior cross-sectional estimates of body composition.
authors.affiliation: CSIRO Human Nutrition, PO Box 10041 BC, Adelaide 5000, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Thomson
authors.forename: Grant D
authors.initials: GD
authors.lastname: Brinkworth
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Buckley
authors.forename: Manny
authors.initials: M
authors.lastname: Noakes
authors.forename: Peter M
authors.initials: PM
authors.lastname: Clifton
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000033:anatomy & histology; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001823:Body Composition / Q000502:physiology*; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D009765:Obesity / Q000503:physiopathology* / Q000628:therapy; D050177:Overweight / Q000503:physiopathology* / Q000628:therapy; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015431:Weight Loss / Q000502:physiology*