Forget the weird diets and exercise, if you want to live longer, just reduce the amount you eat, says British scientist Dr Michael Mosley.

Mosley’s postulation comes after a recent study revealed that consuming 40 percent less could add up to 20 years onto a person’s life span.

A researcher from that study wrote that there is evidence that this theory holds ground after successful research conducted on rats and dogs.

The evidence seems to fit with previous research that has shown that a high metabolic may be a risk factor for earlier death. The metabolic rate is how much energy is used to complete the body’s daily functions.

Mosley believes that the accepted norm of eating three meals a day is only done out of habit and not necessarily because we're actually hungry.

He suggests the key is to follow a restrictive low-calorie diet. Citizens in countries like Japan who follow diets with as little as 600 calories a day tend to live longer than the global average.

"The bottom line is that it is the only thing that’s ever really been shown to prolong life," Mosley said.

"If you stress the body out by restricting calories or fasting, this seems to cause it to adapt and slow the metabolism down. It's a version of 'what doesn't kill you makes you stronger'."

Mosley has also suggested that irregular fasting could be the key to decreasing the production of a growth hormone called IGF-1 large amounts of which are linked to cancer and ageing.