title: Bioelectrical impedance vs. four-compartment model to assess body fat change in overweight adults.
abstract: OBJECTIVE
  The Tanita TBF-305 body fat analyzer is marketed for home and clinical use and is based on the principles of leg-to-leg bioelectrical impedance analysis (BIA). Few studies have investigated the ability of leg-to-leg BIA to detect change in percentage fat mass (%FM) over time. Our objective was to determine the ability of leg-to-leg BIA vs. the four-compartment (4C) model to detect small changes in %FM in overweight adults.
  
  
  METHODS
  Thirty-eight overweight adults (BMI, 25.0 to 29.9 kg/m2; age, 18 to 44 years; 31 women) participated in a 6-month, randomized, double-blind, placebo-controlled study of a nutritional supplement. Body composition was measured at 0 and 6 months using the Tanita TBF-305 body fat analyzer [using equations derived by the manufacturer (%FM(T-Man)) and by Jebb et al. (%FM(T-Jebb))] and the 4C model (%FM(4C)).
  
  
  RESULTS
  Subjects in the experimental group lost 0.9%FM(4C) (p = 0.03), a loss that did not reach significance using leg-to-leg BIA (0.6%FM(T-Man), p = 0.151; 0.6%FM(T-Jebb), p = 0.144). We observed large standard deviations (SDs) in the mean difference in %FM between the 4C model and the Tanita(Manufacturer) (2.5%) and Tanita(Jebb) (2.2%). Ten subjects fell outside +/-1 SD of the mean differences at 0 and 6 months; those individuals were younger and shorter than those within +/-1 SD.
  
  
  CONCLUSIONS
  Leg-to-leg BIA performed reasonably well in predicting decreases in %FM in this group of overweight adults but resulted in wide SDs vs. %FM(4C) in individuals. Cross-sectional determinations of %FM of overweight individuals using leg-to-leg BIA should be interpreted with caution.
authors.affiliation: Department of Family Relations and Applied Nutrition, University of Guelph, 50 Stone Road E, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Chouinard
authors.forename: Dale A
authors.initials: DA
authors.lastname: Schoeller
authors.forename: Abigail C
authors.initials: AC
authors.lastname: Watras
authors.forename: R Randall
authors.initials: RR
authors.lastname: Clark
authors.forename: Rachel N
authors.initials: RN
authors.lastname: Close
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Buchholz
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D004311:Double-Blind Method; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D008954:Models, Biological; D009765:Obesity / Q000175:diagnosis / Q000503:physiopathology; D050177:Overweight / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity