More than a billion adults around the world are at risk of serious disease through lack of exercise, a study has shown.

Investigators found that in 2016 more than a quarter of the global population - 1.4 billion people - were insufficiently active.

As a result, they faced an increased risk of heart and artery disease, Type 2 diabetes, dementia, and some cancers.

The research conducted by the World Health Organisation shows there was little progress in improving physical activity levels between 2001 and 2016.

If current trends continue, the global target of reducing sedentary lifestyle by 10% by 2025 will not be met, said the scientists.

Study leader Dr Regina Guthold, from the WHO in Switzerland, said: "Unlike other major global health risks, levels of insufficient physical activity are not falling worldwide, on average, and over a quarter of all adults are not reaching the recommended levels of physical activity for good health."