Heidi Wicks

Obesity rates in Canada tripled between 1985 and 2011, from 6% to 18%, with significant increases in the very obese 

categories; it is projected that approximately 21% of Canadian adults will be obese by 2019, according to an article published today in CMAJ Open http://cmajopen.ca/content/2/1/E18.full.

Obesity, defined as a body mass index (BMI) of 30 or higher, has substantial adverse health risks such as high blood pressure, diabetes and cancer. As well, obesity has an associated annual cost in Canada estimated at between $4.6 and $7.1 billion.

Normal weight is classified as BMI 18.5–24.9, overweight as BMI 25.0–29.9, obesity class 1 as BMI 30.0–34.9, obesity class II as BMI 35.0–39.9 and obesity class III as BMI 40 or over.

"Although class I obesity appears to be increasing at a slower rate in Canada, the rate for the higher classes of obesity continue to increase disproportionately, a finding consistent with other studies," writes Dr. L.K. Twells, Associate professor, School of Pharmacy and Faculty of Medicine, Memorial University, St. John's, Newfoundland, with coauthors. "These results raise concern at a policy level, because people in these obesity classes are at a much higher risk of developing complex care needs."

Canadian researchers looked at national and provincial data from a number of Canadian health surveys conducted between 1985 and 2011 to determine historical, present and future trends, useful information for examining whether initiatives to reduce obesity have been successful. The analysis is based on self-reported heights and weights, which have been shown to underestimate BMI and therefore obesity rates. The current data are therefore most likely an underestimation of these rates although the trends are accurate.

The study shows some worrying trends. Although every province had increased obesity rates, some had greater increases than others. Obesity rates were lower in the west and higher in the eastern provinces, with Newfoundland and Labrador and New Brunswick having the highest rates.

In general, people over age 40 years were more likely than younger people to be overweight or obese.

Some national trends:

• Between 1985 and 2011, obesity rates increased 200% (from 6% to 18%).

• Specifically, obesity class 1 rates increased 157% (from 5% to 13%), obesity class II rates increased 350% (0.8% to 3.6%) and obese class III rates increased 433% (0.3% to 1.6%).

• Between 2000 and 2011, all provinces had increased rates in obesity classes I, II (except Saskatchewan) and III.

• Newfoundland and Labrador had the highest rates of class I obesity, New Brunswick and Nova Scotia had the highest rates of obese class II (5.7%), and New Brunswick had the highest rates of class III (2.8%).

By 2019:

• Twenty-one percent of Canadians are projected to be obese, although this percentage will vary by province, from 15.7% in British Columbia to 34.6% in Newfoundland and Labrador.

• There will be more overweight and obese than normal-weight adults living in Newfoundland and Labrador, Nova Scotia, New Brunswick, Saskatchewan and Manitoba.

The authors suggest that although national, provincial and local initiatives exist to encourage healthy lifestyles and weight management, it is difficult to know which strategies are effective without a detailed analysis.

"One potential challenge to country-wide initiatives in Canada stems from the fact that although the publicly funded health system is governed by federal legislation, the Canada Health Act (CHA), the actual provision of health services comes under provincial and territorial jurisdiction," the authors write.

"An improved understanding of why such substantial interprovincial variations exist is necessary, including a focus on evaluating existing policies, programs and approaches to the prevention, management and treatment of obesity," conclude the authors.

CMAJ Open, an online open-access journal that publishes high-quality medical and health research, comes from the same family as the Canadian Medical Association Journal (CMAJ).

Read the full research paper: Current and predicted prevalence of obesity in Canada: a trend analysis http://cmajopen.ca/content/2/1/E18.full