Body fatness and bioelectrical impedance in non-obese pre-menarcheal girls: comparison to anthropometry and evaluation of predictive equations

Abstract

Objectives: To determine in non-obese pre-menarcheal girls if bioelectrical impedance (BIA) is a better predictor of body fatness than triceps skinfold (TSF) or body mass index (BMI) and to cross-validate published equations for determination of fat-free mass (FFM) from BIA in pre-menarcheal girls. Design: Cross-sectional analysis of data from 132 non-obese pre-menarcheal girls. The relationship of percent body fat (%BF), derived from isotopic dilution of H 2 18 O to TSF, BMI, and %BF by BIA, calculated from measures of height, weight and resistance was examined by correlation analysis. Setting: Massachusetts Institute of Technology (MIT) Clinical Research Center in Cambridge, MA, USA. Subjects: Pre-menarcheal girls aged 8±12 y were recruited from local schools, MIT summer day camp and by word of mouth. Results: TSF accounted for 68% of the explained variance (R 2 ) in the prediction of %BF measured by H 2 18 O, compared to 38% for BMI and 70% for BIA. Prediction of FFM by comparison of published equations was evaluated in this population. The predictive ability differed by Tanner stage. Kushner's equation (Kushner et al, 1992), based solely on height 2 /resistance was the only equation that provided estimates that did not differ signi®cantly from measured values among all Tanner stages.Conclusions: BIA appears to be a valid and reliable measure of FFM but is no better than TSF in predictions of body fat. Sponsorship: Studies were conducted at the General Clinical Research Center at MIT and were supported by NIH grants RR-00088, DK-HD50537, and DK46200.

Four-component model of body composition in children: density and hydration of fat-free mass and comparison with simpler models

“…Mineral deposition was apparent over the age range we studied and is believed to be completed in early adulthood (31). FFM hydration was significantly higher than in adults; however, although previous work has shown similar results (32,33), investigators continue to use adult-derived values in 2C models used to study children (36). The ratio of mineral to protein also differed significantly by Ϸ20% from that in adults, but the magnitude of this difference was not sufficient to cause error when the adult value was used in combination with a 3C model to estimate hydration and density of FFM.…”

Foot-to-foot bioelectrical impedance analysis: a valuable tool for the measurement of body composition in children

“…It has been recommended that an equation be validated on each different BIA analyser and for each population in which it is to be used. 4,12,20 When considering validation of BIA it is important to understand the statistical methods used. Many authors only report the correlation between BIA and the reference method and this can be misleading as it does not test the equivalence of the results given by the different methods.…”

“…4 ± 12 The few studies that have examined its ability to predict percentage body fat (PBF) found that BIA was superior to BMI and that BIA was similar to SFT performed by trained observers. 4,5,13,14 BIA is painless, requires less training and is subject to less interobserver variation than SFT measurement. 6 Conventional BIA requires careful placement of electrodes on the arm and leg.…”

Body composition of healthy 7- and 8-year-old children and a comparison with the ‘reference child’

“…Thus, differences in the proportion of these components might be masked by BMI, which is dependent on weight and height. Bandini et al 16 have also reported a low accuracy of BMI compared with skinfolds when estimating fatness in pre-pubertal children.…”