We’ve long been told that smoking, eating junk food and being physically inactive are bad for our health, but just how bad are they?

According to a new study, unhealthy lifestyle habits are shortening Canadians’ lives by an average of six years

What’s more, Canadians who live extra healthy lives and follow recommendations for healthy lifestyles have average life expectancies 17.9 years longer than those with the unhealthiest behaviours.

The study was led by Dr. Doug Manuel, a senior scientist at The Ottawa Hospital and at the Institute for Clinical Evaluative Sciences. His team found that smoking, poor diet, physical inactivity, and unhealthy alcohol consumption contribute to 50 per cent of deaths in Canada.

“Unhealthy behaviours place a major burden on Canadian life expectancies,” Manuel said in a statement. “This study identified which behaviours pose the biggest threat.”

Using data from ICES and the Statistics Canada 2009-2010 Canadian Community Health Survey, the study found:

  • 26 per cent of all deaths are attributable to smoking
  • 24 per cent of all deaths are attributable to physical inactivity
  • 12 per cent of all deaths are attributable to poor diet
  • 0.4 per cent of all deaths are attributable to unhealthy alcohol consumption

For men, smoking was the top risk factor, and reduced life expectancy by an average of 3.1 years.

For women, a lack of physical activity was the biggest risk to health, and represented a loss of three years of life.

The researchers also found that Canadians who followed recommended healthy behaviours had a life expectancy 17.9 years greater than individuals with the unhealthiest behaviours.

The full results appear in PLOS Medicine.

The authors acknowledge that using health surveys to assess behaviours has limitations since these surveys are usually telephone-based and use self-reported diet, which tends to be unreliable. But the researchers say they adjusted for the fact that many people misreport their food and alcohol intake.

Dr. Manuel and his team have created an online calculator called Project Big Life to help Canadians estimate their own life expectancy based on habits and lifestyle choices.

The study was funded by the Institute for Clinical Evaluative Sciences and the Ontario Ministry of Health and Long-Term Care.