Validity of Adiposity Indices for Detecting High Body Fat Mass in Mexican Schoolchildren: Results From the NUTRENTO Project

Introduction

Body mass index (BMI) is a known indicator of adiposity. However, alternative measures have recently been proposed in children. We aimed to evaluate the validity of alternative adiposity indices (AIs)—BMI according to the World Health Organization (BMI-WHO) and the International Obesity Task Force (BMI-IOTF) standards, waist circumference (WC), and waist-to-height ratio (WHtR)—in detecting high body fat (HBF) in Mexican schoolchildren.

Methods

This cross-sectional analysis was conducted among 2189 schoolchildren in Hidalgo, Mexico. AIs including BMI-WHO, BMI-IOTF, WC, and WHtR were evaluated via anthropometry. Body fat (BF) was assessed using bioelectrical impedance analysis (BIA). The ability of the AIs to predict HBF was evaluated using sensitivity, specificity, and confidence intervals (95% CI). Agreements between AIs and BF were analyzed using Kappa correlation coefficients and Bland–Altman plots.

Results

In detecting HBF, BMI-WHO showed a sensitivity of 98.2% (95% CI: 97.0–99.0) and a specificity of 59.3% (95% CI: 56.7–61.9), and WHtR showed 98.0% (95% CI: 96.6–98.8) and 57.4% (95% CI: 54.8–59.9), respectively. Among boys, moderate agreement was observed between HBF and BMI-WHO (Kappa = 0.52), WHtR (Kappa = 0.50), and WC (Kappa = 0.47), all with p < 0.001. Among girls, moderate agreement was found with BMI-WHO (Kappa = 0.45) and WHtR (Kappa = 0.41), also with p < 0.001. Bland–Altman analysis showed good agreement between HBF and WHtR and intermediate agreement with BMI-WHO.

Conclusion

BMI-WHO and WHtR demonstrate high validity for assessing HBF in schoolchildren. WHtR may serve as a practical alternative for routine screening and for evaluating the impact of interventions aimed at reducing risks associated with excessive BF accumulation.