Frequent fast-food consumption is associated with weight gain therefore it is hypothesized that relative availability of fast-food is a risk factor for obesity. This thesis examined the association between the neighbourhood-level density of fast-food outlets and adult body mass index (BMI) in Canada. Population-based data on BMI and socio-economic variables from the 2008 Canadian Community Health Survey [CCHS] and selected neighbourhood-level socio-economic data from 2006 Canadian Census were merged with a commercial database containing geographic locations of all restaurants in Canada. The association between BMI and fast-food density (per 10,000 people in CCHS respondent’s FSA) was analyzed using ordinary least squares regression. Spatial clustering of BMI was also investigated and spatial-regression analysis was conducted. FSA-level fast-food density is significantly associated with BMI in Canadian adults, predominantly in females and non-rural area. This population-based analysis established that availability of fast-food restaurants is an important risk factor for obesity in Canada