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Abroad look at Canadian cities suggests that when it comes to your weight, you are where you eat.

Researchers at the University of Alberta have put together an obesity map they say comes from a common-sense idea.

"Several people have pointed it out as a possible or likely cause for increasing obesity rates; that is, that increasing the access to fast food or poor-quality foods might somehow be contributing," health economics professor Sean Cash said.

He and his fellow researchers decided to put that idea to the test by combining obesity figures from cities across the country with the density of the most popular fast-food restaurants. The research was completed earlier this year and recently presented in poster form at a conference of the Agricultural Institute of Canada.

"We found there was actually a fairly strong relationship, a strong correlation, between the two, that those cities that had higher obesity and overweight rates tended to have a higher density of at least the larger fast-food restaurant chains, so there were more restaurants per person in those cities," Prof. Cash said.

Vancouver and Montreal were the cities with the lowest density of these restaurants, less than two for every 10,000 people. Those cities also had lower incidences of obesity.

The areas with higher density, or 3.5 to four restaurants for every 10,000 people, tended to be in the East.

"We found that some of the highest rates of obesity and overweight [people] in Canada, according to Statistics Canada, were in Atlantic provinces - cities like St. John's, with over 36 per cent of the population estimated to be obese."

Prof. Cash cautions that the study simply shows a correlation; it doesn't explain why the two things are connected. He says further study is needed to see whether the availability of restaurants actually causes more people to eat fast food or whether the restaurants purposely set up in places where people already tend to be heavier.

"All we can say from our study is that looking across cities, there is a very strong relationship between where the fast-food restaurants are more densely located and those higher rates of obesity."

Ian Janssen, a population health professor who studies obesity at Queen's University, said that while the study seems to provide intuitive results, it's done on such a broad scale it needs to be interpreted with caution.

"The results that you get when you look across areas can sometimes be misleading in terms of when you look within a given area or within a given region, you can actually see completely different findings," he said.

"There could be all of these other things going on in these cities outside of fast-food restaurants and restaurants that are causing higher obesity rates," Prof. Janssen said. For example, differences in socioeconomic status or physical activity could be directly related to people's weight.

Although he tried to adjust for income levels in compiling the results, Prof. Cash agrees much more work needs to be done on the topic. Plans are under way at the university to launch a more local study.

Both researchers say the main point of the map should be to prompt further research.