title: Comparison of body fatness measurements by near-infrared reactance and dual-energy X-ray absorptiometry in normal-weight and obese black and white women.
abstract: The aim of the present study was to compare body fat percent (BF %) using single-site near-IR reactance (NIR) and dual-energy X-ray absorptiometry (DXA) in a cohort of normal-weight (BMI < 25 kg/m2) black (n 102) and white (n 71); and obese (BMI > or = 30 kg/m2) black (n 117) and white (n 41) South African women (18-45 years). NIR-derived BF % was significantly correlated with DXA-derived BF % in all groups: normal-weight black (r 0.55, 95 % CI: 0.40, 0.67, P < 0.001) and white (r 0.69, 95 % CI: 0.53, 0.79, P < 0.001) women; obese black (r 0.59, 95 % CI: 0.46, 0.70, P < 0.001) and white (r 0.56, 95 % CI: 0.30, 0.74, P < 0.001) women. NIR under-predicted BF% compared to DXA in black women (normal-weight, - 4.36 (sd 4.13) % and obese, - 3.41 (sd 3.72) %), while smaller mean differences were observed in white women (normal-weight, - 0.29 (sd 4.19) % and obese, - 0.81 (sd 3.09) %), irrespective of normal-weight or obese status (P < 0.001). In obese subjects, NIR-derived BF % did not measure values greater than approximately 45 %, while the maximum DXA-derived measure was 58 %. In conclusion, although there was a significant relationship between NIR- and DXA-derived BF %, NIR under-predicted BF % in normal-weight and obese black South African women compared to DXA, but to a greater extent in subjects with very high levels of adiposity (>45 %). The results of single-site NIR as a measure of BF % should therefore be interpreted with caution, particularly in women of African descent and in those with very high levels of adiposity.
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, PO Box 115, Newlands 7725, Cape Town, South Africa.
authors.forename: Courtney L
authors.initials: CL
authors.lastname: Jennings
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Micklesfield
authors.forename: Mike I
authors.initials: MI
authors.lastname: Lambert
authors.forename: Estelle V
authors.initials: EV
authors.lastname: Lambert
authors.forename: Malcolm
authors.initials: M
authors.lastname: Collins
authors.forename: Julia H
authors.initials: JH
authors.lastname: Goedecke
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000273:Adipose Tissue / Q000502:physiology*; D050154:Adiposity / Q000208:ethnology / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D044383:Black People; D005260:Female; D006801:Humans; D007259:Infrared Rays; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis* / Q000208:ethnology; D012016:Reference Values; D013019:South Africa; D013057:Spectrum Analysis / Q000379:methods; D044465:White People; D055815:Young Adult