Scientists at Seattle Children's Research Institute in the US used geographic information system (GIS) data to assess the availability of supermarkets and fast-food restaurants across Seattle and San Diego, as well as the proximity of parks and other green spaces.
They found that children who lived in neighbourhoods with plenty of opportunities for walking and physical activity had a 59 per cent lower chance of being obese, compared with those in areas with few green spaces.
Eight per cent of youngsters in areas with good physical activity and nutrition environments were obese, compared with 16 per cent in areas with poorer environments.
Lead researcher Dr Brian Saelens, whose findings are published in the American Journal of Preventive Medicine, said: "People think of childhood obesity and immediately think about an individual's physical activity and nutrition behaviours, but they do not necessarily equate obesity with where people live."
The expert added that parents and policymakers should pay more attention to postcodes "because they could have a big impact on weight".
Figures from the National Child Measurement Programme for England indicate that 22.6 per cent of four to five-year-olds and 33.4 per cent of ten to 11-year-olds were overweight or obese during the 2010-11 school year.