Lack of physical activity could be causing as many deaths worldwide as smoking and obesity do, say researchers who are calling on people to take at least a 15-minute brisk walk each day.

This week's issue of the medical journal The Lancet includes a series of studies leading up to the London Olympics to highlight how little physical activity most people worldwide actually get and how dire the health consequences are.

Researchers want adults worldwide to sit less and move more to gain health benefits. (Eric Thayer/Reuters)

I-Min Lee from Brigham and Women's Hospital in Boston and her co-authors estimated that worldwide, physical inactivity causes six per cent of the burden of disease from coronary heart disease, seven per cent of Type 2 diabetes, 10 per cent of breast cancer, and 10 per cent of colon cancer.

What’s more, physical inactivity was blamed for nine per cent of premature mortality — more than 5.3 million deaths of the 57 million deaths globally in 2008.

Eliminating physical inactivity could increase life expectancy by 0.68 years. That may seem small, they said, but the gains are for the whole population, not just inactive people who start moving more.

Canadian health authorities recommend that adults get 2½ hours of physical activity a week.

Tanya Berry holds a Canada Research Chair in physical activity promotion at the University of Alberta in Edmonton. Berry said her research suggests half of Canadians think they're moving enough, but they're mistaken.

"If you actually put a little accelerometer or pedometer on people, something that actually objectively measures how active they are, it's closer to 15 per cent are actually active and 85 per cent of Canadians are not active enough to achieve health benefits."

The Lancet researchers said people need to be told about the dangers of being sedentary, rather than just the benefits of exercise. They urged governments to find ways to make physical activity more convenient, affordable and safer.

"This series emphasizes the need to focus on population physical activity levels as an outcome, not just decreasing obesity," Harold Kohl, a professor of epidemiology at the University of Texas and one of the Lancet authors, said in a release.

Kohl recommended prioritizing physical activity across sectors including health, transportation, sports, education and business.

Min-Lee and her co-authors acknowledged that not everyone is capable of being physically active.

"This summer, we will admire the breathtaking feats of athletes competing in the 2012 Olympic Games," the researchers concluded.

"Although only the smallest fraction of the population will attain these heights, the overwhelming majority of us are able to be physically active at very modest levels — 15 to 30 minutes a day of brisk walking — which bring substantial health benefits."

With files from CBC's Brandy Yanchyk