Fat-Free Mass Predictions From Anthropometrics in South African Prepubertal Children.

Fourteen prediction equations for fat-free mass were developed using anthropometric measurements in a sample of South African children aged 6-9 years.

• The development sample comprised 117 children (51% Black; 55% boys; mean age 7.9 ± 0.8 years).
• Equations contained five to nine variables each.
• R² range across the 14 equations was 0.88–0.92.
• Bioelectrical impedance analysis-derived fat-free mass was used as the reference measure in multivariable regression models.

Four of the developed equations were strongly correlated with dual-energy X-ray absorptiometry-derived fat-free mass in an external validation sample of Black prepubertal children.

• The validation sample consisted of 75 Black prepubertal children with a mean age of 8.5 ± 1.3 years.
• All four equations showed strong correlation with DXA-derived fat-free mass (r > 0.95; p < 0.001).
• Dual-energy X-ray absorptiometry was used as the reference standard for external validation.

Three of the four externally validated equations yielded fat-free mass estimates with acceptable agreement compared to DXA-derived fat-free mass.

• Mean differences for the three equations ranged from 0.16 to 0.94 kg.
• Limits of agreement were ±5 kg for these three equations.
• Agreement was assessed using Bland-Altman plots.
• Relationships and mean differences were also assessed using Pearson's correlation and independent t-tests, respectively.

Bioelectrical impedance analysis was identified as limited by cost, availability, and lack of local validation for use in South African children.

• South African children face a double burden of malnutrition from both undernutrition and rising obesity.
• Fat-free mass is described as a key health indicator.
• The study aimed to provide an alternative to BIA using simple anthropometric measurements suitable for low-resource settings.