By 2015, obesity is projected to overtake smoking as the most common risk for heart disease in Canada, according to a study published in CMAJ Open.The article also states that the overall risk of heart disease is set to decrease slightly over the next seven years.

Although heart disease is a leading cause of death in this country, killing more than 70 000 people a year, there has been no clear picture of its effect into the future.

To start filling in this picture, the study's authors created a model that simulated the future lives of 22.5 million Canadians aged 20 years and older. The model projects the prevalence of five risk factors associated with heart disease: obesity, smoking, diabetes, high cholesterol and uncontrolled high blood pressure.

After running the numbers, the project team concludes that in 2015, obesity will surpass smoking as the most common risk for heart disease. In 2003, it passed high blood pressure.

"Obesity is a major problem in Canada, affecting nearly one in five adults," said lead author Dr. Doug Manuel, a senior scientist at the Ottawa Hospital Research Institute. "Our study suggests that the escalating rates of obesity and diabetes are counteracting gains in population health being made in other areas, such as smoking and high blood pressure."

Although the model projects the rise of obesity and diabetes, Dr. Manuel notes that, for the individual, neither risk factor is as hazardous as smoking.

"There is also some good news here," adds Dr. Manuel, who is also an associate professor with the Faculty of Medicine at the University of Ottawa. "For the first time we have credible evidence that the rate of heart disease is set to decline in Canada as a result of progress in controlling high blood pressure and cholesterol levels, and helping people to stop smoking."

Overall, the study projects a modest decline among Canadian adults in the risk factors that lead to heart disease, suggesting a decreasing rate of the disease between now and 2021.

"The prevalence of risk factors could be lower than our projections if healthy physical and social conditions improve," writes Dr. Manuel and co-authors, which included researchers from Statistics Canada and three Canadian universities. "Conversely, Canada's physical and social environment may become more conducive to an increase in obesity."

The Public Health Agency of Canada estimates that more than five million Canadian adults are obese and that obesity-related illnesses cost the country's health care system $4 billion a year.