A lack of exercise is now causing as many deaths as smoking across the world, a study suggests.
The report, published in the Lancet to coincide with the build-up to the Olympics, estimates that about a third of adults are not doing enough physical activity, causing 5.3m deaths a year.
That equates to about one in 10 deaths from diseases such as heart disease, diabetes and breast and colon cancer.
Researchers said the problem was now so bad it should be treated as a pandemic.
And they said tackling it required a new way of thinking, suggesting the public needed to be warned about the dangers of inactivity rather than just reminded of the benefits of it.
The team of 33 researchers drawn from centres across the world also said governments needed to look at ways to make physical activity more convenient, affordable and safer.
It is recommended that adults do 150 minutes of moderate exercise , such as brisk walking, cycling or gardening, each week.