Publication date: 2011
What is already known about this subject:
- Lower physical activity and greater screen time are associated with higher body mass index (BMI), a measure of body fat, in children and adolescents. However the reported strength of the associations varies with age and primary outcome of interest. In order to better understand these associations, long term studies are required.
- An examination of the interrelationships between BMI, physical activity and screen viewing behaviours was undertaken in the Raine Study Gen2 participants from 6 to 14 years.
- It is unclear whether reported associations between the variable of interest track from childhood into adolescence.
What this study adds
- Analyses were based on data for 1403 Gen2 adolescents who participated in the 14 year survey. Physical activity and screen time were reported by parents at, 6, 8 and 10 year follow-ups, and by the adolescent at 14 years. BMI was derived from height and weight measures taken at each survey. Sedentary patterns of behaviour when young predicted later and concurrent obesity.
- The prevalence of unhealthy behaviours in childhood was higher among obese adolescents. Relationships changed over time, however a critical window exists between 6 and 10 years. Physical activity, rather than screen time, is predictive of BMI, once adolescent.
- This paper confirms the direction of screen time, BMI and physical activity influences. Results highlight the importance of establishing healthy behaviours in the early years as many children are already overweight, high screen users and low active at 6 years. Different intervention targets are required for children and adolescents.