Detection of overweight and obesity in a national sample of 6–12-y-old Swiss children: accuracy and validity of reference values for body mass index from the US Centers for Disease Control and Prevention and the International Obesity Task Force

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Abstract
Background: For defining overweight in children, reference values for body mass index (BMI) are available from the US Centers for Disease Control and Prevention (CDC) and the International Obesity Task Force (IOTF). However, these 2 sets of reference criteria differ, and their accuracy in classifying adiposity has not yet been validated in most countries. Objective: We compared BMI criteria from the IOTF and the CDC with percentage of body fat (%BF) from multisite skinfold thicknesses (SFTs) for identification of overweight in 6–12-y-old Swiss children. Design: In a representative sample (n = 2431), weight, height, and 4 SFTs were measured. Regression and receiver operating characteristic (ROC) curves were used to evaluate BMI as an indicator of adiposity. Results: BMI and %BF were well correlated (r2 = 0.74), and the areas under the ROC curves for overweight and obesity were 0.956–0.992. The sensitivity and specificity of the IOTF and CDC overweight criteria and of the CDC obesity criteria were high. The sensitivity of the IOTF obesity criteria was only 48% and 62% in boys and girls, respectively. Overall, the performance of the CDC criteria was superior. With the use of the CDC criteria, the prevalence of overweight in girls and boys was 19.1% and 20.3%, respectively. Conclusions: BMI is an excellent proxy measure of adiposity in 6–12-y-old children. In Swiss children, both BMI criteria accurately predict overweight, but the sensitivity of the IOTF obesity criteria is poor. They failed to detect one-half of the children identified as obese on the basis of %BF from SFTs.