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Updated: Jul 14, 2026
Assessment of Child Anthropometry in a Large Epidemiologic Study
Published on: February 2, 2017
Impedance index or standard anthropometric measurements, which is the better variable for predicting fat-free mass in
Quang Dung Nguyen1, Gerhard Fusch, Sven Armbrust
1Department of Neonatology and Pediatric Intensive Care, University Children's Hospital, Greifswald, Germany.
Insights
The impedance index (ZI) is the best single predictor of fat-free mass (FFM) in children, outperforming anthropometric measurements. Adding weight to ZI further improves FFM prediction accuracy.
Area of Science:
- Pediatric Nutrition
- Body Composition Analysis
- Biometrics
Background:
- Accurate estimation of fat-free mass (FFM) is crucial for assessing pediatric growth and nutritional status.
- Traditional anthropometric measurements have limitations in predicting FFM accurately.
- Bioelectrical impedance analysis (BIA) offers a non-invasive method for body composition assessment.
Purpose of the Study:
- To compare the predictive efficacy of the impedance index (ZI) against various anthropometric measurements for estimating FFM in children.
- To determine the optimal combination of variables for predicting FFM using BIA and anthropometry.
Main Methods:
- Dual-energy X-ray absorptiometry (DXA) was used as the criterion method to measure FFM in 120 white children (ages 2.5-18 years).
- Measurements included weight, height, mid-upper arm circumference (MUAC), skinfold thicknesses, and bioelectrical impedance.
- Stepwise multiple regression analysis identified significant predictors of FFM.
Main Results:
- The impedance index (ZI) was the strongest single predictor of FFM, explaining 96.2% of the variance (r=0.981).
- Incorporating weight into the ZI model enhanced FFM prediction to 96.6% (r=0.983).
- Body Mass Index (BMI) and MUAC demonstrated the weakest predictive power for FFM.
Conclusions:
- The impedance index (ZI) significantly outperforms anthropometric measurements as a standalone predictor of FFM in pediatric populations.
- Combining bioelectrical impedance analysis with weight measurement provides improved accuracy for FFM estimation in children.
Aim:
To compare the predictive value of impedance index (ZI, height2/impedance) with anthropometric measurements for estimating fat-free mass (FFM).
Methods:
FFM of 120 white paediatric children (46 males, 74 females), aged 2.5-18 years was measured by using dual energy X-ray absorptiometry. Weight, height, mid-upper arm circumference (MUAC), skinfold thickness (biceps, triceps, subscapular and suprailiac) and bioelectrical impedance were also obtained. Stepwise multiple regression analysis and residual plots were performed to determine the most significant variables to predict FFM.
Results:
The single best predictor of FFM was ZI, which explained 96.2% of the variance in FFM (r = 0.981, SEE = 2.15 kg). Addition of weight to the model containing ZI increased the explained variance of FFM to 96.6% (r = 0.983, SEE = 2.03 kg). BMI and MUAC were the poorest predictors of FFM: r = 0.422, SEE = 10.2 kg and r = 0.621, SEE = 8.93 kg, respectively.
Conclusion:
Impedance index is a more significant single predictor of FFM than other anthropometric measurements. The predictive accuracy of bioelectrical impedance analysis-based prediction equations for FFM was improved by addition of weight.
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