Overweight and obesity in 4-year-old South Australian children and the stability of IOTF cut points in this age group

Objective: To assess the validity of internationally accepted mid-year cut points for overweight and obesity in children and their application for ongoing surveillance. Data: A large (n = 114,925) state wide administrative data set of preschool children (aged 48-60 months) in South Australia including measured height and weight, collected at various points in the fifth year of life by the Children, Youth and Women's Health Service (CYWHS) between 1995 and 2003. Methods: Prevalence of overweight and obesity were calculated for each year of the data set between 1995 and 2003. The international mid-year cut points were compared to cut points for each month of age throughout the fifth year of life. Results: The prevalence of overweight and obesity in this age group has increased significantly over the period for both males and females. The estimates of overweight and obesity prevalence for both males and females calculated using the mid-year cut points were not significantly different to cut points for each month of age in both genders. Conclusions: The body mass index of children does not vary significantly through the fifth year of life and prevalence estimates can be obtained at any point in the fifth or sixth year of age for surveillance purposes.