Sitting for long periods increases the risk of diabetes, heart disease and death, researchers suggest.

The scientists from Leicester and Loughborough Universities say harm is done even if people also exercise.

The study, published in Diabetologia, analysed 18 existing studies involving almost 800,000 people.

Diabetes UK said anyone who spent a lot of time sitting or lying down would "obviously benefit" from moving more.

The researchers say the opportunities for sedentary behaviour in modern society such as watching TV, sitting in a car or using a computer are "ubiquitous".

Of course, in modern society many people head to the gym for a burst of exercise to redress the balance.

But the research team, led by Dr Emma Wilmot from the Diabetes Group at the University of Leicester, says while going to the gym or pool after work is better than heading straight for the sofa, spending a long time sitting down remains bad for you.