Linking childhood obesity to the built environment: a multi-level analysis of home and school neighbourhood factors associated with body mass index.

OBJECTIVES This study examines environmental factors associated with BMI (body mass index) levels among adolescents with the aim of identifying potential interventions for reducing childhood obesity. METHODS Students (n=1,048) aged 10-14 years at 28 schools in London, ON, completed a survey providing information on age, sex, height, weight, home address, etc., which was used to construct age-sex adjusted BMI z-scores. The presence of recreation opportunities, fast-food outlets and convenience stores was assessed using four areal units around each participant's home and school neighbourhood: "circular buffers" encompassing territory within a straight-line distance of 500 m and 1000 m; and "network buffers" of 500 m and 1000 m measured along the street network. School neighbourhoods were also assessed using school-specific "walksheds". Multilevel structural equation modeling techniques were employed to simultaneously test the effects of school-environment (Level 2) and home-environment (Level 1) predictors on BMI z-scores. RESULTS Most participants (71%) had a normal BMI, 16.9% were overweight, 7.6% were obese, and 4.6% were considered underweight. Multilevel analyses indicated that built environment characteristics around children's homes and schools had a modest but significant effect on their BMI. The presence of public recreation opportunities within a 500 m network distance of home was associated with lower BMI z-scores (p<0.05), and fast-food outlets within the school walkshed was associated with higher BMI z-scores (p<0.05). CONCLUSION Interventions and policies that improve children's access to publicly provided recreation opportunities near home and that mitigate the concentration of fast-food outlets close to schools may be key to promoting healthy lifestyles and reducing childhood obesity.