Obesity is now pandemic, affecting millions of people worldwide.1 In rich countries, between 10% and 20% of people are obese, and the problem is not unknown even in poor countries.1 In the United States, the National Institutes of Health and the surgeon general have acknowledged the importance of the problem and are developing public health strategies to curb the epidemic.2,3
Obesity is a condition of excessive body fat that results from a chronic energy imbalance whereby intake exceeds expenditure. Excess body fat increases an individual's risk of premature death from chronic diseases such as coronary heart disease, stroke, type 2 diabetes mellitus, gallbladder disease and some cancers.2 The direct medical costs attributable to adult obesity in Canada are estimated to have been $1.8 billion in 1997, or 2.4% of total direct medical costs.4 Thus, the public health burden of obesity and related disorders is great.
The World Health Organization recommends the continued surveillance of the population prevalence of obesity using body mass index (BMI, calculated as kg/m2) as the indicator.
There is recent evidence that there have been large increases in the national prevalence of overweight and obesity in Canadian children and adults over the last 2 decades, similar to the increases observed in other industrialized nations.5,6 Although the causes of this are not well defined, lack of physical activity may be an important factor.7
The purpose of this report is to present obesity surveillance maps for Canadian adults (aged ≥ 20 years) from 1985 to 1998 in an effort to describe the dramatic increases in the prevalence of obesity that have occurred at both the national and provincial levels. Data concerning BMI were obtained from a series of 5 population surveys that collected self- reported heights and weights. The surveys included the 1985 and 1990 Health Promotion Surveys and the 1994, 1996 and 1998 National Population Health Surveys.8,9,10,11,12 The prevalence of adult obesity in each of the samples was computed (defined as BMI ≥ 30 kg/m2) and weighted to be representative of the Canadian population for the year each survey was conducted. Given that individuals (particularly obese individuals) tend to underreport their body weights,13 the prevalences of obesity reported here should be considered conservative.
Canadian obesity surveillance maps developed from the survey data are presented in Fig. 1. The overall national prevalence of obesity increased across the surveys, more than doubling over the 13-year period: 5.6%, 9.2%, 13.4%, 12.7% and 14.8% for the years 1985, 1990, 1994, 1996 and 1998 respectively. In 1998, the adult population of Canada was 22.2 million;14 thus, the prevalence of obesity in that year translates into 3.3 million obese Canadians. The maps clearly show the progression of the obesity epidemic across the country. Over the 13-year span considered here, all provinces experienced increases in the prevalence of obesity. By 1998, only Quebec and British Columbia had prevalences below 15%, although they were not far behind — both had a prevalence of obesity of 12%. Unfortunately, data for the territories are lacking in the surveys used for this report (Fig. 1). North American Aboriginal populations have an increased risk of obesity and associated disorders;15 thus, obesity surveillance in Northern Canada is a research priority.
Similar obesity surveillance maps have been developed for the United States using self-reported data from the Behavioral Risk Factor Surveillance System (BRFSS).16,17 The prevalence of obesity in the United States increased from 12% in 1991 to 17.9% in 1998.16 As was the case in Canada, the prevalence of obesity increased in all regions of the United States. A more recent analysis from the BRFSS indicates that the prevalence of obesity among US adults was 19.8% in 2000, demonstrating a continued increase.17
In summary, Canada has recently experienced a major epidemic of obesity, with the population prevalence more than doubling between 1985 and 1998. In 1998, the problem of obesity was nationwide, because it did not appear to be limited to one province or region. Continued population surveillance of obesity is necessary to determine the extent of the problem and to estimate its impact on the present and future health of Canadians.