A striking new Canadian study reveals our worst health habits and most beloved vices — smoking, lazing about, eating junk food and drinking booze — contribute to around half of all deaths in Canada, and shave an estimated six years off the life expectancy of men and women.

“We know these things affect your health — but the impact is massive,” says lead author Dr. Doug Manuel, a senior scientist at The Ottawa Hospital and professor at the University of Ottawa, and a senior core scientist at the Institute for Clinical Evaluative Sciences.

The findings informed the development of an online life expectancy calculator, ProjectBigLife.ca, which crunches your health and lifestyle data to reveal your personal projected life expectancy.

Publishedthis month in PLOS Medicine, a peer-reviewed journal, the study pegged smoking as the top health hazard to Canadians.

The team also provided exclusive data to the Star, which reveals just how many years of life Canadians lose with each bad habit.

Smoking slashes an estimated 2.8 years off of Canadians’ lives, according to the researchers. Physical inactivity is next, at around 2.6 years of lost lifespan, followed by 1.2 years for poor diet and around 2 weeks for alcohol.

The research is based on an algorithm Manuel and his team created to analyze data from the Institute for Clinical Evaluative Sciences and the Statistics Canada 2009 to 2010 Canadian Community Health Survey.

Manuel was careful to point out these are population-based numbers — meaning the individual impacts of bad habits such as smoking are much higher, since only around 20 per cent of Canada’s total population actually smokes.

Calculating the life expectancy for individuals is more complicated, but ProjectBigLife.ca takes into account everything from your fruit and vegetable intake to the amount of physical activity you get in a week. “This is considerably more complex than, say, how your doctor is currently calculating your heart disease risk,” Manuel says.

Let’s say you’re a 40-year-old woman living in downtown Toronto. You quit smoking a decade ago, but you still drink with your friends every weekend. You eat a fairly balanced diet and go for a run three times a week. You don’t have any chronic conditions — yet. So how long are you going to live?

For this imaginary Torontonian, her life expectancy would be nearly 88 years, according to the calculator.

People can even input their postal codes, which helps predict geographic variations, including pollution levels.

“With these algorithms, we’re able to look at the combined effect,” says Manuel. “Many of us are unhealthy in multiple aspects.”

A variety of other factors come into play as well, says Manuel. “For individual people, we’re seeing that your neighbourhood, your education, these are really influential as well … we’re seeing really marked inequities,” he says.

Smoking

Overall life expectancy loss for Canadians: 2.8 years

With more than a quarter of all deaths attributable to smoking, there’s no question this is the biggest health risk facing Canadians.

“It’s something we’ve known about for a long time. Study after study shows this is the case,” says Dr. Brett Belchetz, a Toronto emergency room physician.

But what’s also worth keeping in mind is not just quantity of life, but the quality of life as well. Belchetz says smoking impacts someone’s ability to participate in physical activities, and leads to higher rates of life-impairing conditions like lung or heart disease.

The bottom line: Butt out, already.

Poor diet

Overall life expectancy loss for Canadians: 1.2 years

An unhealthy diet is another big risk factor, but Kitchener-based registered dietitian Andrea D’Ambrosio says people can put themselves on a path to healthier eating with some small changes.

Start by writing down what you eat in a day to get a sense of your own habits, she says. Are you cooking at home, or eating out? Are you getting enough vegetables, or relying on fast-food?

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“It’s important to encourage Canadians and consumers to get back to the kitchen,” says D’Ambrosio, owner of Dietetic Directions. “We need to understand that if we take the time to cook balanced meals and put together lunches, we’ll really make an impact on cutting back on the sugar, fat, etc.”

The bottom line: Cook balanced meals more often, eat out less.

Physical inactivity

Overall life expectancy loss for Canadians: 2.6 years

The dangers of being sedentary are increasingly well-known, and this latest study highlights just how impactful physical inactivity can be on your health.

So how do you get moving more often? Gidon Gabbay, founder and president of Toronto-based G Force Home Training, says joining a gym or taking a class with a friend can give you a sense of accountability.

“Set realistic goals for yourself that are both short and long term,” he adds. “Achieving milestones, even if they’re small, will create a cycle of motivation that makes positive lifestyle habits stick.”

The bottom line: Sit less, move more.

Unhealthy drinking

Overall life expectancy loss for Canadians: 2 weeks

Is a glass of wine a day good for you, or is booze all bad? It seems like there’s a new study every week blaming or praising alcohol. While the research is hard to parse, Belchetz says this latest study shows other factors — smoking, diet, and physical activity — are more important to focus on.

When it comes to drinking, he says it’s all about moderation, meaning no more than a couple glasses of wine or beer, or one to two ounces of liquor, in a day.

“If you’re regularly consuming more than that, or binge drinking on a small numbers of occasions, you are at risk for a number of other health conditions,” he says.

The bottom line: The more you drink, the more you’re at risk.

Correction - August 29, 2016: This article was edited from a previous version that misspelled Dr. Brett Belchetz's surname.