Baseline measures for a school-based obesity control programme: Project Energize: differences by ethnicity, rurality, age and school socio-economic status.

AIM School-based interventions to tackle the rise in childhood overweight and obesity remain inconclusive and are often limited in their application to diverse populations. To inform and measure the effect of the implementation of a primary school-based longitudinal randomised controlled nutrition and activity intervention, Project Energize, baseline measures of body size and blood pressure were required. METHODS This cross-sectional study stratified by age, sex, ethnicity, rurality and school socio-economic-status (school-SES) measured body mass index (BMI), percentage body fat (%BF), waist and resting blood pressure from 2752 5- and 10-year-old children (62% European, 31% Māori) representative of the Waikato region of New Zealand. RESULT Waikato children have a high prevalence of overweight and obesity that is linked with hypertension. Cardiovascular risk factors including raised blood pressure and hypertension, waist and arm circumference and percentage body fat (%BF) were more prevalent in 10-year-olds, lower school-SES and to some extent, urban living. In European children, BMI and waist circumference were similarly predictive of %BF, but for Māori children, waist circumference predicted %BF better than BMI. CONCLUSIONS A variety of stratified, baseline measurements is important when designing school-based interventions. In particular, waist circumference measures may be a more accurate predictor of %BF than BMI when determining measurement protocols that consider different ethnic groups and environments among children. The effect of targeted improvements of the school physical activity and nutrition environment on the rate of increase of weight, fatness and blood pressure in children should be examined.