Developing an Impedance Based Equation for Fat-Free Mass of Black Preadolescent South African Children
Open accessAbstract
Bioelectrical impedance analysis (BIA) is a practical alternative to dual-energy X-ray absorptiometry (DXA) for determining body composition in children. Currently, there are no population specific equations available for predicting fat-free mass (FFM) in South African populations. We determined agreement between fat-free mass measured by DXA (FFMDXA) and FFM calculated from published multi-frequency bioelectrical impedance prediction equations (FFMBIA); and developed a new equation for predicting FFM for preadolescent black South African children. Cross-sectional data on a convenience sample of 84 children (mean age 8.5 ± 1.4 years; 44 {52%} girls) included body composition assessed using Dual X-ray Absorptiometry (FFMDXA) and impedance values obtained from the Seca mBCA 514 Medical Body Composition analyzer used to calculate FFM using 17 published prediction equations (FFMBIA). Only two equations yielded FFM estimates that were similar to the DXA readings (p > 0.05). According to the Bland–Altman analysis, the mean differences in FFM (kg) were 0.15 (LOA: −2.68; 2.37) and 0.01 (LOA: −2.68; 2.66). Our new prediction equation, F F M = 105.20 + 0.807 × S e x + 0.174 × W e i g h t + 0.01 × R e a c t a n c e + 15.71 × log ( R I ) , yielded an adjusted R2 = 0.9544. No statistical shrinkage was observed during cross-validation. A new equation enables the BIA-based prediction of FFM in the assessment of preadolescent black South African children.
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Considering segmental technology for under 18 years old, five equations are available for estimating FFM in both sexes.
“Considering segmental technology, five equations are available for estimating FFM in both sexes [43–45, 57, 74].”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
Methods §2.4 (page unavailable) says the authors used 17 published BIA equations developed for boys and girls aged 5–10, supporting the availability of FFM equations for both sexes. The Introduction mentions segmental BIA, but the paper does not say that five equations are available for segmental technology or for under-18s generally. The five equations in Results §3.1 are those that underestimated FFM, not a count of segmental equations. (LLM, conf=0.82)
Experimental — accuracy not yet measuredRegarding segmental technology for under 18 years old, five equations are suitable for both sexes.
“Regarding segmental technology, five are suitable for both sexes [43–45, 57, 74].”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
The Results (§3.2; page unavailable) give one fat-free-mass equation with sex coded for girls and boys, developed for black South African preadolescents. The Methods (§2.4; page unavailable) identify the device as multi-frequency BIA, but our copy does not establish that this equation uses segmental measurements. The paper supports one equation for both sexes in a narrower population, not its suitability across all under-18s or the group total of five. (LLM, conf=0.82)
Experimental — accuracy not yet measuredOut of the 19 equations for under 18 years old, seven were developed using segmental technology.
“Out of the 19 equations, 12 were developed using foot to hand technology [37, 55, 58, 59, 72, 73, 75, 76, 100] and seven equations were developed using segmental technology [43–45, 57, 74].”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
The Introduction and Methods (§2.4; page unavailable) describe a new equation for children developed using measurements from a multi-frequency Seca mBCA 514 analyzer. They do not explicitly classify that equation as developed using segmental technology or substantiate the citing document’s tally of seven out of 19 equations. (LLM, conf=0.76)
Experimental — accuracy not yet measuredFour predictive equations for under 18 years old were developed with multifrequency devices but at the frequency of 50 kHz.
“All 19 equations were developed at a single frequency of 50 kHz, although four predictive equations were developed with multifrequency devices but at the frequency of 50 kHz [43, 44, 57].”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
Methods §2.4 (page not supplied) says the authors used a multifrequency device to obtain 50 kHz measurements for their new equation and to evaluate 17 published equations for children. It does not say that four equations were originally developed with multifrequency devices at 50 kHz; measurements used to evaluate an equation do not establish how it was developed. (LLM, conf=0.85)
Experimental — accuracy not yet measuredConcerns with applicability were high in 19 studies.
“Concerns with applicability were high in 19 studies [37, 42–59] and unclear [41, 50, 60–69] in 12 studies due to the restricted sample size.”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
The remaining 12 studies on subjects under 18 years old were performed in different countries around the world and included both sexes.
“Two of these studies were conducted in the USA, where no female participants were involved [55, 76], while the remaining 12 studies were performed in different countries around the world with both sexes included [37, 43–45, 57–59, 72–75, 100].”
From High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review (2024) · cites this paper as [43]
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“Regarding segmental technology, five are suitable for both sexes [43–45, 57, 74].”
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Fat‐Free Mass Predictions From Anthropometrics in South African Prepubertal Children
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- Authors
- van Zyl, A., White, Z., Ferreira, J., & Wenhold, F. A. M.
- Affiliations
- Department Human Nutrition, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia 0007, South Africa
- University of Pretoria (ZA)
- Corresponding author
- White, Zelda
- Venue
- Nutrients
- Publisher
- MDPI AG
- Published
- 2019-08-28
- Volume
- 11
- Issue
- 9
- Pages
- 2021
- ISSN
- 2072-6643 (ISSN-L)
- PMC
- PMC6769520
- OpenAlex
- W2970928542
- Cited by
- 13
- References
- 45
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 4 · 2023: 3 · 2022: 1 · 2021: 1
- FWCI
- 0.34
- Type
- journal article
- Language
- en
- Open access
- gold
- dx.doi.org
- Licence
- Locations
- Nutrients (publishedVersion, cc-by)
- Europe PMC (PubMed Central) (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- UpSpace Institutional Repository (University of Pretoria) (submittedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- Arcadia Fund
- University of Pretoria
- Topics
- Health Sciences › Medicine › Physiology › Body Composition Measurement Techniques
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Obesity, Physical Activity, Diet
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Electrical and Bioimpedance Tomography
- Keywords
- bioelectrical impedance analysis, fat-free mass, prediction equations, preadolescents, black South African children, body composition, reactance, resistance index, sex differences
- MeSH terms
- Age Factors, Body Composition, Child, Cross-Sectional Studies, Female, Humans, Male, Models, Biological, Predictive Value of Tests, South Africa, Reproducibility of Results, Absorptiometry, Photon, Electric Impedance, Black People
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