Introduction: Reducing childhood obesity in Australia must include preventive action1 to keep children in a healthy weight, as well as programs to reduce weight of those already in the overweight range. Understanding the epidemiology of weight progression throughout childhood may assist in designing interventions.
Methods: We investigated the persistence of weight status between early childhood and late adolescence using 7 waves of data from the Longitudinal Study of Australian Kindergarten cohort, including 4983 children and 27602 body mass index (BMI) measurements within 12 years of follow up, to age 16/17 years. We determined persistence of healthy weight and unhealthy weight between adjacent waves, based on WHO definitions. Additionally, for children in healthy weight at age 4/5 years, we used survival analysis to determine significant demographic predictors of duration of health weight, after controlling for child BMI-z and maternal BMI.
Results: At age 4/5 years, 3270 (66%) children were in a healthy weight and 1637 (33%) were above a healthy weight. Healthy weight was more persistent than unhealthy weight. Movement from unhealthy weight to healthy weight was greatest between age 4/5 years and 6/7 years (33% of children). Persistence of healthy weight was not affected by gender or Indigenous status (p>0.05). Children of lower socio-economic position (SEP) and those whose main language spoken was not English had higher risk of moving into unhealthy weight (22% and 27%). Higher BMI-z at age 4/5 years (yet still healthy weight), was the strongest predictor of moving into unhealthy weight before adolescence (hazard ratio=2.3 [ 95% CI 2.0-2.6]).
Conclusion: Opportunities for interventions to reduce overweight may be best before age 7 years. For maintenance of healthy weight, targeted prevention programs should address low SEP groups, culturally and linguistically diverse communities and children who are in the upper end of healthy weight as pre-schoolers.