Study: Body mass index in urban Canada

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Consistent evidence suggests that the prevalence of obese and overweight people is increasing rapidly around the world in both developing and developed countries, including Canada.

The speed at which this change is occurring suggests our everyday environments and routine modern behaviours might underlie the rise in obesity, rather than a change in the genetic profile of the population.

Between 1981 and 1996, the prevalence of combined obese and overweight people in Canada rose from 48% to 57% among men and from 30% to 35% among women. Rates rose in all provinces.

This study, published recently in the American Journal of Public Health, explored links between body mass index for adults and certain individual characteristics, such as income level, diet patterns and stress, as well as immigrant status and the impact of characteristics of the neighbourhoods and cities in which people live.

Its findings suggest that urban environments in Canada play a small but significant role in shaping the distribution of body mass index.

The study, which used data from the 2001 Census and Statistics Canada's 2000/2001 Canadian Community Health Survey, found that body mass index was strongly related to social position (for example, income and education levels).

The overwhelming amount of variation in body mass index occurred at the individual level for both men and women. However, the study found that neighbourhood and metropolitan area environments registered small incremental effects on body mass index for both genders.

For both men and women, living in a neighbourhood with residents of low educational attainment meant that they had a significantly higher body mass index, regardless of their own educational attainment. This finding may reflect norms and practices around diet and exercise in those neighborhoods, but might also be related to issues of neighborhood safety, availability and quality of recreational opportunities.

For men, living in a sprawling metropolitan area had an incremental influence on body mass, over and above individual and neighbourhood characteristics. The finding linking urban sprawl to overweight and obesity has been shown in the United States by other researchers. However, this was the first time such a connection has been made in Canadian cities.

Note: Body mass index (BMI) is calculated by dividing weight in kilograms by height in metres squared. For adults, a BMI of 25 or more indicates the person is overweight; 30 or more indicates obesity. An adult male who is 1.8 metres tall (five-foot-10) and weighs 95 kg (210 pounds) would have a BMI of 30 and be considered obese.

The study "Body mass index in urban Canada: Neighbourhood and metropolitan area effects" was published in the March 2007 edition of the American Journal of Public Health. It was prepared by a team of analysts from the Department of Geography at McGill University, Montréal, and analysts in the Health Analysis and Measurement Group at Statistics Canada. An abstract of the article is available online for free (http://www.ajph.org/) in English only. The full text of the article is also available online.

For more information, or to enquire about the concepts, methods or data quality of this release, contact Nancy Ross (514-398-4307; nancy.ross@mcgill.ca), McGill University.