We have long been warned of the dangers of smoking cigarettes but a new study suggests lack of exercise is just as deadly.
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According to researchers at Harvard Medical School, one in 10 deaths worldwide could be prevented if people exercised more - and that number rose to one in six in the UK.
In their study, published in The Lancet, scientists estimated that a lack of exercise is responsible for the deaths of 90,000 Britons each year, while smoking-related deaths total around 100,000.
The researchers claim our sedentary lifestyle contributes directly to one in five bowel cancer deaths, one in six from breast cancer and one in 10 from heart disease.
It is thought only a third of Brits take the NHS recommended two-and-a-half hours of exercise a week, despite the fact that walking, gardening and even housework are included as sufficient.
Lead researcher Dr I-Min Lee said: "Am I surprised that it's comparable to smoking, no. Only about one quarter of the world's population smoke but about two thirds are inactive.
"The UK is doing worse than the world average. We're not sure why this is but only about a third are taking the recommended amount. It could be to do with the weather. There is also a lack of infrastructure to encourage people to walk and cycle."
Dr Lee, who pointed out that her figures were only estimated, also said she hoped those who avoided exercise would one day be regarded as "social pariahs", just as smokers often are.
She added: "Tobacco has done it successfully. Many years ago most people smoked but now you are a pariah if you smoke."
However, campaigners insist that quitting smoking is still the best way to prevent cancer.
Dr Claire Knight, health information manager at Cancer Research UK, told the Daily Mail: "When it comes to preventing cancer, stopping smoking is by far the most important thing you can do.
"Smoking is responsible for over 60,000 cases of the disease each year in the UK, making it the biggest preventable cause of cancer.
"But the role of physical activity in cancer prevention shouldn't be underestimated."
What do you think? Is it the weather that stops Brits getting enough exercise? Leave your comments below...