Lack of exercise is now causing as many deaths as smoking across the world, a new study has revealed.

The report, published in the Lancet, claims that about a third of adults are not doing enough physical activity, causing 5.3million deaths a year.

That accounts to about one in 10 deaths from diseases such as heart disease, diabetes and breast and colon cancer.

Researchers said that the problem was now so severe that it should be treated as a pandemic, the BBC reported.

And they said that tackling it required a new way of thinking, suggesting the public needed to be warned about the dangers of inactivity rather than just being reminded of the benefits of it.

The team comprising of 33 researchers, drawn from centres across the world, also said that governments needed to look at ways to make physical activity more convenient, affordable and safer.

It is recommended that adults exercise moderately for 150 minutes, by brisk walking, cycling or gardening, each week.

The Lancet study found that people in higher income countries were the least active with those in the UK among the worst as nearly two thirds of adults were judged not to be doing enough.

Although the researchers admitted comparisons between countries were difficult because the way activity was estimated may have differed from place to place.

Nonetheless, they said that they remained confident that their overall conclusion was valid.

"The global challenge is clear - make physical activity a public health priority throughout the world to improve health and reduce the burden of disease." Pedro Hallal, one of the lead researchers, said.

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