Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please "contact us" to request a format other than those available.
Adult obesity in Canada: Measured height and weight
by Michael Tjepkema
Majority overweight or obese
The percentage of Canadians who are overweight or obese has risen dramatically in recent years, mirroring a worldwide phenomenon.1, 2, 3, 4 The health consequences of excess weight are well known. It is a risk factor for type 2 diabetes, cardiovascular disease, high blood pressure, osteoarthritis, some cancers and gallbladder disease.5, 6, 7 As well, psychosocial problems, functional limitations and disabilities are associated with excess weight.5, 8
For more than a decade, information about the weight of Canadians has been based on self-reports, that is, survey respondents reported their own height and weight rather than being measured and weighed. However, such data are known to underestimate the prevalence of overweight and obesity.9, 10, 11, 12 The 2004 Canadian Community Health Survey: Nutrition (CCHS), which directly measured respondents’ height and weight, makes it possible to draw a more accurate picture (see Data sources and analytical techniques).
According to the 2004 CCHS, 23.1% of Canadians aged 18 or older, an estimated 5.5 million adults, had a body mass index (BMI) of 30 or more, indicating that they were obese (Table 1) (see What is BMI?). This is significantly higher than estimates derived from self-reported data collected in 2003, which yield an obesity rate of 15.2% (see Methodology makes a difference). Another 8.6 million, or 36.1%, were overweight.
Among people who are obese, BMIs vary greatly. As a result, obesity is divided into three categories, with successive values representing escalating health risks. People in Class I (BMI 30.0 to 34.9) have a high risk of developing health problems. For those in Class II (BMI 35.0 to 39.9), the risk is very high, and in Class III (BMI 40 or more), extremely high. In 2004, 15.2% of Canadian adults had a BMI in Class I; 5.1% were in Class II, and 2.7%, in Class III (Table 1).
In 1978/79, the Canada Health Survey collected measured height and weight data for a nationally representative sample of adults. That year, the age-adjusted obesity rate was 13.8%, far below the 2004 rate of 23.1% (Table 2). The increase was evident in each of the three obesity categories, especially Class II and Class III. The proportion of adults in Class II went from 2.3% to 5.1%; in Class III, from 0.9% to 2.7%
The obesity rate of every age group except 65 to 74 rose during this period (Chart 1). The most striking increases were among people younger than 35 and 75 or older. For instance, the percentage of 25- to 34-year-olds who were obese more than doubled, rising from 8.5% in 1978/79 to 20.5% in 2004. The extent of the increase among people aged 75 or older was about the same: from 10.6% to 23.6%.
The average BMI of adults rose from 25.1 in 1978/79 to 27.0 in 2004, and the BMI distribution of the adult population shifted toward the heavy end of the continuum (Chart 2).
In 2004, men and women were equally likely to be obese: 22.9% and 23.2%, respectively. However, when the three obesity categories are examined separately, a difference between the sexes emerges. A higher percentage of women than men were in Class III (Table 1, Chart 3).
For both sexes, obesity rates were lowest at ages 18 to 24 (10.7% of men and 12.1% of women), and peaked around 30% among 45- to 64-year-olds (Chart 4). The percentage of seniors who were obese was lower at about 25%.
With a few notable exceptions, obesity rates did not vary greatly by province (Chart 5). In 2004, men’s rate was significantly above the national level (22.9%) in Newfoundland and Labrador (33.3%) and Manitoba (30.4%). Women’s rate surpassed the national figure (23.2%) in Newfoundland and Labrador (34.5%), Nova Scotia (30.3%) and Saskatchewan (32.9%).
While Canada’s obesity rates have, for the most part, been based on self-reported data, the United States has derived rates from actual measurements of height and weight since the early 1960s. With the directly measured data from the 2004 CCHS, it is possible to compare the prevalence of obesity in the two countries.
Age-standardized results show that 29.7% of Americans aged 18 or older were obese in 1999-2002, significantly above the 2004 figure for Canada (23.1%). Most of this difference was attributable to the situation among women. Whereas 23.2% of Canadian women were obese, the figure for American women was 32.6%. As well, each obesity category (Class I, II and III) accounted for a higher percentage of American than Canadian women (Table 3). The difference in obesity rates between American and Canadian women prevailed in all age groups except 45 to 54 and 75 or older (Chart 6).
The obesity rate of Canadian men was 22.9%, significantly below the age-adjusted American rate of 26.7%. However, this was mainly a reflection of Class III obesity: American men were much more likely to have a BMI of 40 or more. The percentages of Canadian and American men whose BMI put them in Class I or II were statistically similar. American men aged 18 to 24, 35 to 44 and 65 to 74 were more likely than their Canadian counterparts to be obese (Chart 7).
The racial make-up of the two countries might explain some of the differences, as research has shown that obesity rates vary by ethnic origin.13 Nonetheless, when obesity rates of White Americans and Canadians are compared, White women in the United States were significantly more likely than those in Canada to be obese: 30.3% versus 24.8% (Table 3) (see Definitions). However, the percentages of White American and Canadian men who were obese did not differ.
In Canada, people of Aboriginal origin (off-reserve) had a significantly high obesity rate—37.6%—about 1.6 times higher than the national average (Tables A, B and C). These results are consistent with other research based on self-reported data.13
As might be expected, the likelihood of being obese was related to diet and exercise. Men and women who ate fruit and vegetables less than three times a day were more likely to be obese than were those who consumed such foods five or more times a day (Chart 8). Although other factors may be driving this relationship, the association persisted when age and socio-economic status were taken into account. Another study has also shown obesity to be independently associated with infrequent consumption of fruit and vegetables.14 However, because the CCHS data are cross-sectional, the direction of this relationship cannot be determined (see Limitations).
Physical activity, too, was related to the prevalence of obesity. People whose leisure-time was sedentary were more likely than those who were physically active to be obese. For example, 27.0% of sedentary men were obese, compared with 19.6% of active men. Among women, obesity rates were high not only for those who were sedentary, but also for those who were moderately active (Chart 9). These relationships remained statistically significant when adjustments were made to account for age and socio-economic status.
Obesity rates varied by marital status for women, but not for men (Chart 10). About a quarter of married men and women aged 25 or older were obese. The rate was significantly higher among women who were widowed (30.0%). By contrast, the percentages of married, separated/divorced, widowed and never-married men who were obese were not significantly different.
The association between education and obesity was not straightforward. Men aged 25 to 64 with no more than secondary graduation had significantly high obesity rates, compared with men who were postsecondary graduates (Chart 11). Among women, those with less than secondary graduation were more likely than postsecondary graduates to be obese. As well, the obesity rate of women who had some, but had not completed, postsecondary education was high.
Men in lower-middle income households were less likely to be obese than were those in the highest income households. For women, those in middle and upper-middle income households had significantly elevated obesity rates, compared with women in the highest income households (Chart 12). When age was taken into account, the results for men persisted, but for women, only those in middle-income households had a significantly high obesity rate.
Being overweight or obese is a risk factor for a number of chronic conditions. Analysis of CCHS data reveals associations between excess weight and high blood pressure, diabetes, and heart disease.
A high BMI is a risk factor for type 2 diabetes.15 Just 2.1% of men whose BMI was in the normal range reported having diabetes; the figure was 3.7% among overweight men, and almost tripled (to at least 11%) among those who were obese (Chart 14). The pattern was similar for women. And even when the effects of the other factors were taken into consideration, men and women who were obese had significantly high odds of reporting diabetes (Table 5).
The prevalence of heart disease increased with BMI among men. While 2.8% of men with a normal BMI reported having heart disease, the figure was 6.0% among men who were overweight and almost 8% among those who were obese (Chart 15). Even when age, marital status, education, household income, smoking, and leisure-time physical activity were taken into account, the association between BMI and heart disease among men remained (Table 5).
For women, the prevalence of heart disease did not differ significantly by BMI, except for those in obese Class I who were slightly more likely to have it than were women whose BMI was in the normal range. But when the other demographic, socio-economic and lifestyle factors were considered, this relationship disappeared.
Although it has generally been known that obesity rates have risen dramatically in Canada over the past quarter century, the extent of the increase was uncertain, because estimates relied on self-reported data. Results from the 2004 Canadian Community Health Survey: Nutrition (CCHS), based on directly measured height and weight, indicate that 23% of adults were obese. This was up from 14% in 1978/79, but still below the obesity rate in the United States (30%). However, in 2004, another 36% of Canadians were overweight. Consequently, a majority of Canadians—almost 60%—were in a weight range that increased their risk of developing health problems. In fact, according to results of the CCHS, as BMI increases, so does the likelihood of having high blood pressure, diabetes and heart disease. And for many people, further weight gain is probable. Longitudinal research has shown that those who are overweight are far more likely to continue to gain weight than to lose it.16
The author thanks Wayne Millar for his help in producing the variance estimates for the 1978/79 Canada Health Survey and the 1999-2002 National Health and Nutrition Survey based on SUDAAN.
You need to use the free Adobe Reader to view PDF documents. To view (open) these files, simply click on the link. To download (save) them, right-click on the link. Note that if you are using Internet Explorer or AOL, PDF documents sometimes do not open properly. See Troubleshooting PDFs. PDF documents may not be accessible by some devices. For more information, visit the Adobe website or contact us for assistance.