Association between anthropometric indices and body fat for identifying excess body fat in elementary school children: a population-based cross-sectional study.

All four anthropometric indices showed high discriminatory ability for identifying excess body fat in children, with ROC AUCs exceeding 0.9 in most cases.

• Participants included 660 children aged 9-12 years (349 boys and 311 girls).
• The areas under the ROC curve (AUCs) and 95% CIs for BMI, degree of obesity, waist circumference, and waist-to-height ratio were >0.9 in both sexes in most cases.
• Excess body fat was defined as body fat percentage exceeding the 85th, 90th, or 95th percentile.
• Body fat was assessed using bioelectrical impedance analysis.

BMI and degree of obesity demonstrated strong precision-recall performance for identifying excess body fat.

• PR AUCs and 95% CIs for BMI and degree of obesity were ≥0.8 in most cases.
• Precision, recall, and F1 scores for BMI and degree of obesity in identifying obesity at the 85th or 95th percentiles were >70% in nearly all cases.
• PR curve analysis was used alongside ROC curve analysis to evaluate discriminatory ability.

BMI showed substantial agreement with body fat percentage-defined obesity at the 85th and 90th percentiles, while degree of obesity showed moderate agreement.

• Kappa coefficients indicated substantial agreement between BMI and the 85th or 90th percentiles of body fat percentage.
• Kappa coefficients indicated moderate agreement for the degree of obesity.
• The Matthews correlation coefficient (MCC) index showed a pattern similar to that of the kappa coefficients.
• Classification performance was evaluated using a confusion matrix, accuracy, precision, recall, F1 score, Cohen's kappa coefficient, and MCC.

The study used multiple complementary statistical approaches to evaluate the classification performance of anthropometric indices against body fat percentage.

• Receiver operating characteristic (ROC) curve and precision-recall (PR) curve analyses were both employed.
• Classification performance was further evaluated using confusion matrix, accuracy, precision, recall, F1 score, Cohen's kappa coefficient, and Matthews correlation coefficient.
• The study was a population-based cross-sectional design.
• Fat mass, fat-free mass, and body fat percentage were assessed using bioelectrical impedance analysis.

Identifying and managing obesity in children is considered essential to prevent obesity-related diseases in adulthood.

• The study evaluated four anthropometric indices: BMI, degree of obesity, waist circumference, and waist-to-height ratio.
• The sample consisted of 660 elementary school children aged 9-12 years.
• The study was designed to evaluate associations between these indices and body fat, particularly excess body fat.