The original version of the 5:2 said some of the best results came from fasting for about 12 hours from breakfast to dinner.

But Dr Mosley said some people ended up getting “a bit irritable”.

The new regime sets out plans for three meals a day. And it suggests a 24 hour period of “fasting” - on 800 calories a day, could start with an early dinner, followed by a late breakfast, to allow around 13 hours without food overnight.

A number of studies have suggested that short periods of fasting can help control blood sugar levels - reducing the risk of type 2 diabetes.

“What I'd recommend is that you have a slightly earlier supper on the evening before, and then a slighter later breakfast on the fasting day. That way, you'll be fasting for 13 hours or more overnight,” he said.

Adherents of the diet are thought to include singer Beyoncé while a number of politicians, including then chancellor George Osborne have used it to shed pounds.