This research project is part of the 'Cities for Better Health Childhood Obesity Prevention Initiative' (CBH COPI). The objective of the CBH COPI initiative is to develop, implement, and evaluate the effectiveness of a package of prevention interventions in five cities to promote healthy eating, physical activity, a positive health-related quality of life, and a reduction in rates living with overweight or obesity among children aged 6-13 years in six cities across Australia, Brazil, Canada, Japan, South Africa and Spain. The primary research objective of CBH COPI is to estimate the impact of the intervention packages on the average BMI of the target population of children across the participating countries, at one-year and two-year follow-ups. The secondary research objective is to estimate the impact of the intervention packages on average health-related quality of life (HRQoL) at the same time points. Exploratory aims include estimating the impact of the packages on behaviours related to physical activity and diet.