One-quarter of all adults are classified as completely inactive, meaning they get less than 30 minutes of moderate activity a week.

1.5 billion people around the world are so inactive they are at a greater risk of illness from the likes of heart disease, diabetes, cancer to depression.

Our sedentary living now kills more people than obesity.

It's the subject of a new book, The Miracle Pill: Why a Sedentary world is getting it all wrong.

The book is by Peter Walker, who is a political correspondent for The Guardian in the UK.

He joined Francesca Rudkin to discuss it.