Executive summary: Obesity in Canada

Executive Summary

This report highlights new analyses of the prevalence, determinants and impact of obesity in Canada. The first three chapters describe the prevalence of obesity among adults, children and youth, and Aboriginal Peoples, combining new and existing estimates. This is followed by new analysis of the determinants of obesity, using an innovative measure of risk, and the impact of modifying determinants, as well as an updated estimate of the health and economic costs of obesity. The final chapter summarizes key lessons learned from the international literature on obesity prevention and management.

Prevalence

Over one in four Canadian adults (estimates range from 24.3%-25.4%) are obese, according to measured height and weight data from 2007-2009. Of children and youth aged 6 to 17, 8.6% are obese. Generally, actual measurements of height and weight result in higher estimates of obesity than data obtained from self-reports.

Between 1981 and 2007/09, measured obesity roughly doubled among both males and females in most age groups in the adult and youth categories. Not only has the prevalence of obesity increased over time but obesity is becoming more severe and fitness levels are decreasing as well. Since the late 1970s, for example, increases in the prevalence of obesity have been proportionately greater for the heaviest weight classes. Research also suggests a trend toward increased adiposity and decreased fitness for children, youth and adults.

Obesity varies substantially by geographic area. Obesity prevalence ranges from 3.4% to 34.3% across countries in the Organisation for Economic Co-operation and Development (OECD). New analyses show that the variation in self-reported obesity across health regions within Canada is similarly large, ranging from 5.3% to 35.9%.

As with previous studies, new analysis discussed in this report also show that self-reported obesity remains more prevalent among Aboriginal peoples than in the Canadian non-Aboriginal adult population: for example, 25.7% among off-reserve Aboriginal adults compared with 17.4% among non-Aboriginal adults in Canada (according to self-reported data from the 2007/08 CCHS). On-reserve First Nations groups tend to have a higher prevalence still, with over one-third (36.0%) estimated as obese, based on 2002/03 data. Self-reported obesity among adults is similar for Inuit, off-reserve First Nations, and Métis populations (23.9%, 26.1% and 26.4%, respectively), whereas childhood obesity varies from 16.9% among Métis to 20.0% among off-reserve First Nations to 25.6% among Inuit. The estimated prevalence of obesity among Aboriginal peoples in Canada can be derived from several sources, but no single source offers a complete picture of on- and off-reserve First Nations, Inuit and Métis.

Determinants

Research has identified a number of determinants associated with obesity, including physical activity, diet, socioeconomic status, ethnicity, immigration, and environmental factors. A population health approach to understanding obesity examines both the proximal or more immediate factors linked to obesity, such as diet and activity, as well as more distal factors, such as community and socioeconomic characteristics. However, the patterns involved are complex, and determinants are interconnected; furthermore some factors, such as income and education, tend to give rise to different associations for men than women.

Because risk factors for obesity often occur together, analyses are presented that statistically account for several social determinants of health and health-related behaviours. These analyses, which report their findings in terms of population attributable risk (PAR) and population impact number (PIN), offer insight from a population perspective into the proportion and number of cases of overweight and obesity that may be associated with these determinants.

For example, on the basis of this approach, physical inactivity emerged as most strongly associated with obesity at the population level for both men and women after adjusting for age and other health, behavioural and social determinants. As well, distal or indirect factors such as income, rural residence and minority status continued to have an association with obesity even after controlling for more direct health behaviours, such as inactivity, fruit and vegetable consumption and alcohol use.

Such research, while theoretical, may help to inform to decisions by Canadian policy-makers, health promoters and health care providers on targeting obesity prevention and treatment interventions. However, because these analyses use cross-sectional data and rely on a number of assumptions, they cannot be used to make inferences about the causes of obesity. Our collective understanding of the determinants of obesity will continue to evolve as the effectiveness of policies, programs and interventions are monitored and assessed.

Disease and financial burden

Obesity is an important population health concern. Obesity increases the risk of a number of chronic conditions, such as type 2 diabetes, hypertension, cardiovascular disease, and some forms of cancers. It is also associated with stigma and reduced psychological well-being. Some of these health issues may begin in childhood. Current evidence also suggests that people who are severely obese have a greater risk of premature mortality than those in the normal weight and overweight ranges. Determining the precise number of deaths attributable to obesity is difficult, however, as obesity often co-occurs with other risk factors such as physical inactivity and/or chronic conditions.

It has been estimated that obesity cost the Canadian economy approximately $4.6 billion in 2008, up $735 million or about 19% from $3.9 billion in 2000. This is a conservative estimate, as it is limited to those costs associated with the eight chronic diseases most consistently linked to obesity. Another study using a comparable methodology and looking at 18 chronic diseases estimated the cost to be even higher, at close to $7.1 billion.

Approaches for addressing obesity

A review of the national and international literature found that strategies to combat obesity and address obesogenic environments can be classified into three main categories:

1. Health services and clinical interventions that target individuals;
2. Community-level interventions that directly influence individual and group behaviours; and
3. Public policies that target broad social or environmental determinants.

Like smoking cessation, effective obesity prevention may require a multifaceted, long-term approach involving interventions that operate at multiple levels and in complementary ways.

Relatively few population-level obesity prevention and management interventions – especially public policy approaches that target broader environmental factors – have been systematically evaluated in terms of their effectiveness or cost-effectiveness. Developing and implementing effective interventions will require close and frequent monitoring to identify which approaches work in different settings and with different populations, as well as economic analysis to understand their potential value for money.