Overweight and obesity in 4-5-year-old children in New Zealand: Results from the first 4 years (2009-2012) of the B4School Check programme.

AIM
We describe the prevalence of overweight and obesity in four-year-old children in New Zealand, variations with ethnicity and socio-economic status, and changes over the study duration using body mass index (BMI) measurements collected as part of the B4School Check programme.

METHODS
Demographic and BMI data were extracted for all children measured between 2009 and 2012. Overweight and obesity rates were estimated using International Obesity Task Force (IOTF) 2012 standards and the 85th (overweight) and 95th (obese) percentiles for BMI-for-age of the World Health Organization (WHO) 2006, Centers for Disease Control and Prevention 2000 and UK 1990 reference standards.

RESULTS
A total of 168,744 BMI measurements were included in the analysis with a coverage rate of 66.5%. Mean BMI was 16.30?kg/m(2) in girls and 16.44?kg/m(2) in boys. Mean BMI z-score (WHO 2006 standards) was 0.601 in girls and 0.785 in boys. Using WHO 2006 standards, 16.9% of girls and 19.6% of boys were overweight and 13.8% of girls and 18.7% of boys were obese. Using IOTF standards, 18.3% of girls and 16.2% of boys were overweight and 5.7% of girls and 4.7% of boys were found obese. Prevalence of overweight and obesity was higher in Pacific and Maori children and those living in more socio-economically deprived areas than other children. No definite time-trends were observed over the study duration.

CONCLUSIONS
The study reaffirms the high prevalence of overweight and obesity in pre-school children in New Zealand, and demonstrates the variations in prevalence when using different reference standards.