Introduction: early detection of childhood obesity plays a crucial role in the prevention of diseases during adulthood. At present, the most commonly used screening tool for detecting overweight/obesity in children is the percentile for age of body mass index, although this rate is unable to provide information about fat distribution. An emerging marker of abdominal fat distribution is waist circumference (WC). Objective: the aim of this study was to evaluate the differences between the different diagnostic criteria available to define overweight and obesity in order to establish the optimal WC cut-off values for the Spanish children population. Methods: a cross-sectional study was carried out in 8,241 schoolchildren aged 3 to 12 years from Villanueva de la Cañada (Madrid, Spain). WC (cm), weight (kg) and height (cm) were measured according to the recommendations of the Society for the Advancement of Kineanthropometry (ISAK). The values obtained for the diagnostic criteria (Spanish Orbegozo Foundation (OF), the International Obesity Task Force (IOTF), and the World Health Organization (WHO) were compared using McNemar's test for paired proportions. The kappa coefficient (κ) was used to assess the degree of agreement of the three classifications. We analyzed the validity of body mass index (BMI) and WC using the receiver operating characteristic (ROC) curve analysis. The Youden index was used to determine cut-off values for WC that identify childhood obesity Results: overweight and obesity prevalences were calculated according to the OF, IOTF, and WHO criteria. There was a "substantial" agreement for the overweight and obesity categories between the Spanish criteria and IOTF (κ = 0.636), while agreement was "slight" between the Spanish criteria and those of WHO (κ = 0.198). The estimated cut-off WC criteria ranged from 54.5 to 88.0, varying according to sex and age. Conclusion: the proposed WC cut-off values, stated for the first time in a young Spanish population, are a simple and valid alternative as diagnostic criteria of abdominal obesity.
