Adult obesity prevalence in Canada and the United States
Obesity has been described as a global epidemic. It has been linked to diabetes, hypertension, cardiovascular disease and some forms of cancer. Accurate surveillance of obesity trends is an important step in developing effective strategies to reduce its impact on public health. In the United States, the National Health and Nutrition Examination Survey (NHANES) has been gathering measured height and weight data for years. In 2007, the Canadian Health Measures Survey (CHMS), the most comprehensive health measures survey in Canada, began collecting direct measurements of height, weight, body mass index (BMI), skinfolds and waist circumference from a nationally representative sample of the population. The complementary nature of these surveys has created an opportunity to compare rates of obesity among adults in Canada and the United States.
Among men, the prevalence of obesity was over 8 percentage points lower in Canada than in the United States (24.3% compared with 32.6%) and among women, more than 12 percentage points lower (23.9% compared with 36.2%) (Chart 1).
Prevalence of obesity in adults aged 20 to 79, by sex: Canada, 2007 to 2009 and United States, 2007 to 2008
1Significantly different from estimate for Canada (p < 0.05).
2Use with caution (coefficient of variation 16.6% to 33.3%).
Obesity class estimates do not sum to exact totals due to rounding.
Sources: Centers for Disease Control and Prevention (CDC)/National Center for Health Statistics (NCHS), National Health and Nutrition Examination Survey 2007–2008, and Statistics Canada, Canadian Health Measures Survey 2007 to 2009.
Because the risk of adverse health effects increases at higher levels of body mass index (BMI), obesity is divided into three categories. In all three BMI categories, prevalence was significantly lower in Canada than in the United States. In the highest BMI category the prevalence was twice as high in the United States (6.0%) compared with Canada (3.1%).
Rising obesity prevalence in men and women
Between the late 1980s and today, the prevalence of obesity increased significantly in both the United States and Canada. In Canadian men the prevalence rose by approximately 10 percentage points and among men in the United States, the prevalence rose by 12 percentage points. Among women, the increase was approximately 8 percentage points in Canada and approximately 10 percentage points in the United States
Over the 20-year period, patterns of increase were fairly consistent across age groups in both the United States and Canada. Among men, the increase was highest among those aged 60 to 74. In this age group, obesity increased 17 percentage points in Canada and approximately 18 percentage points in the United States. Among women, the increases were highest among those aged 20 to 39.
In 2007 to 2009, the prevalence of obesity among young and middle-aged Canadian women (aged 20 to 59) was similar to or lower than that observed in U.S. women 20 years earlier.
Comparisons between non-Hispanic white populations
In Canada, almost 26% of the non-Hispanic white population was obese in 2007 to 2009 compared with 33% of the non-Hispanic white population in the United States. Among the heaviest (class III obesity), however, the prevalence was more similar in the two countries (3.5% in Canada and about 5% in the United States).
The difference in obesity prevalence is smaller when non-Hispanic white populations are compared because of the ethnic compositions of each country. In the United States, most of the non-white population is black or Hispanic. Obesity prevalence is higher in these groups than it is in the white population. In Canada, the largest non-white population group is East/Southeast Asian for whom obesity prevalence is lower.
What is BMI?
Body mass index (BMI): Calculated as weight in kilograms (kg) divided by height in meters squared (m2), rounded to one decimal place. For male and female adults aged 20 and over, obesity class I was defined as a BMI of 30.0 to 34.9 kg/m2; obesity class II was defined as a BMI of 35.0 to 39.9 kg/m2; and obesity class III was defined as a BMI of 40.0 kg/m2 or higher.
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