# Correlation Between Age and Body Composition Values Using Bioelectrical Impedance Analysis in Young Children

## TL;DR

This study shows how age and sex affect body composition measurements in young children using bioelectrical impedance analysis.

## Contribution

The study derives new regression equations to estimate body composition in young children using BIA data.

## Key findings

- Fat-free mass is strongly predicted by age and sex in young children.
- Fat mass and phase angle are moderately predicted by age alone.
- Regression equations show high accuracy for fat-free mass (R² = 0.911).

## Abstract

Background and aim: Bioelectrical impedance analysis (BIA) is an attractive method for measuring the fat-free mass (FFM) and fat mass (FM) in adults. Although BIA is not typically performed in young children, previously published prediction equations for BIA in young children have been used recently. The present study evaluated the relationship between age, sex, and body composition in BIAs of young children.

Methods: This study is a retrospective cross-sectional analysis. All patients weighing >8 kg and 12-100 months old were included in the study. The body composition values in the BIA (FFM, FM, and phase angle (PhA)) were calculated. A multiple linear regression analysis for the body composition values in the BIA was used with the variables of age (months) and sex, as well as a constant.

Results: A total of 147 patients (86 boys and 61 girls) with a median age of 47 months were enrolled. Using multiple regression analyses, the FFM equation included the age, sex, and a constant (FFM (kg) = 0.128 × age + 0.391 × sex [male = 1, female = 0] + 6.378 [R2 = 0.911]). The equations for the FM and PhA included the age and a constant (FM (kg) =0.036 × age + 1.094 [R2 = 0.5068], PhA [°] = 0.021 × age + 3.533 [R2 = 0.482]).

Conclusions: The present study demonstrated that age and sex are significant predictors of body composition parameters in young children as measured by BIA. Specifically, FFM was strongly associated with both age and sex, while FM and PhA were moderately associated with age. The derived regression equations may serve as reference models for estimating body composition in pediatric populations using BIA.