Lack of exercise is killing almost as many people as smoking, according to new research published in The Lancet.
Researchers at Harvard say too little exercise is responsible for 10 percent of deaths globally each year — that's 5.3 million of the 57 million deaths each year.
This is because a lack of exercise can lead to people being overweight and obese, which increases their chance of heart disease, diabetes and cancer.
Lead researcher Dr I-Min Lee, from Harvard Medical School, told the UK's Daily Mail that the death rate of obesity is comparable to smoking.
"Only about one quarter of the world's population smoke but about two thirds are inactive," she said.
She said the challenge is to successfully educate people about the dangers of not exercising — as has happened with smoking.
"Tobacco has done it successfully. Many years ago most people smoked but now you are a pariah if you smoke," she said.
In 2009 almost 1050 Australian deaths were attributed to obesity.
The Australian Government Department of Health and Ageing recommends Australian adults get at least 30 minutes of exercise each day on most days of the week.
However more than a third of Australians don't exercise and another third only do a low level of exercise.
Professor Michael Cowley, director of the Obesity and Diabetes Institute at Monash University, told ninemsn he's not surprised by the research.
"We've seen smoking rates come down, yet we haven't seen heart disease rates come down," he said.
"That's probably because the benefit we've seen in terms of cardiac health in terms of smoking reduction has been lost because we've had an increase in cardiac risk because of obesity."