The objectives of this thesis were to examine the relationship between the built environment and obesity-related behaviours in Canadian youth, and to address measurement issues relevant for studying these relationships. The thesis is comprised of four manuscripts. The first manuscript determined the accuracy of the food retailer locations surrounding 34 schools in Ontario as provided by two geographic information system (GIS) databases. The GIS locations of 25% of the food retailers were located within 15 m of their actual location, 50% were within 25 m, and 75% were within 50 m. These values did not differ by GIS database source. The second manuscript examined the association between the presence of food retailers surrounding schools and students’ lunchtime eating behaviours. It also determined whether a circular or road network buffer provided a better geographic boundary of the food retail environment surrounding schools. It was carried out in 6,971 9th and 10th grades students from 158 schools. The presence of food retailers near schools was strongly associated with students regularly eating their lunch at a snack-bar, fast-food restaurant or café. The road network buffers provided the better measure of the food retail environment. The third manuscript determined the optimal buffer size of the food retail environment surrounding schools. Six road network buffers were created around 158 schools. These ranged in size from 500 m to 5000 m. Results indicated that the 1000 m buffer was the optimal size. The fourth manuscript explored associations between urban sprawl and active transportation, moderate to vigorous physical activity (MVPA) and overweight/obesity in 7,017 youth aged 12 to 19 who resided in one of Canada's 33 Census Metropolitan Areas. Increasing levels of sprawl were modestly associated with increased active transportation (only among 12 to 15 year olds) and MVPA. No associations were found for overweight/obesity. Taken together, the results from this thesis provide a better understanding of the role of the built environment on obesity-related behaviours in Canadian youth. Important measurement issues in this topic area were also addressed. / Thesis (Ph.D, Community Health & Epidemiology) -- Queen's University, 2012-01-30 19:36:47.354