Scientists have discovered that dieting slows the ageing process, in mice at least.

Eating a low-calorie diet seems to protect the heart, keeping it healthy and young.

The evidence is based on a laboratory study carried out at the University of Wisconsin-Madison, in the US.

This new research helps us in our quest to get at how the heart ages

Prof Tom Kirkwood, University of Newcastle

Mice given a low-calorie diet had 20% fewer age-related heart changes, says a team led by Dr Tomas Prolla.

Ageing of the heart is associated with certain genetic changes. Adopting a reduced calorie diet in middle age may slow this process by "reprogramming" genes, say the US scientists.

Calorie reduction also appears to prolong the life of cells and dampen down parts of the immune system that can cause tissue damage.

Holy grail

Several previous studies have suggested that restricted diets can have an impact on longevity.

Professor Tom Kirkwood, of the Institute for Ageing and Health at Newcastle University, UK, says it is very important to understand the changes that make an old heart more vulnerable to failure than a young heart.

He told BBC News Online: "This new research helps us in our quest to get at how the heart ages.

"It confirms that an extreme low-calorie diet, which has long been known to slow the ageing process in mice and rats, delays the appearance of age-related changes in the hearts of these animals."

The research is published in the Proceedings of the National Academy of Sciences.