Program SI! is a multi-level, school-based intervention for the promotion of cardiovascular health from early childhood. The aim of this paper is to characterize the prevalence of obesity and high blood pressure in the preschoolers enrolled in the study, and to compare various criteria for classifying obesity.

The study was a cluster-randomized controlled intervention trial including 24 state schools in Madrid (Spain). Weight, height, triceps and subscapular skinfold thicknesses, waist circumference, and systolic and diastolic blood pressure were measured in 2011 children (1009 boys and 1002 girls) aged 3 to 5 years (3.7 [0.9]). Body mass index and blood pressure were classified by corresponding task force criteria. Obesity was studied by 6 different criteria. Associations of body mass index, body weight, body fat, and waist circumference on blood pressure were examined, and the risk of high blood pressure in relation to tertiles of body mass index was calculated.

The prevalence of obesity according to the International Obesity Task Force varied from 2% at age 3 to 8% at age 5, and the overall prevalence of high blood pressure (≥ 90th percentile) was 20%. Sex- and age-specific criteria for obesity showed better agreement with the reference than a single generalized cutoff. The risk of high blood pressure was higher for the highest tertile of body mass index distribution.

The highest prevalence of obesity and high blood pressure was found among older children. The classification of obesity in children was more accurate using sex- and age-specific cutoffs.