The secret of extending life by decades may lie in switching off certain genes, scientists believe, after showing that small genetic tweaks can make organisms live 60 per cent longer.

Ten years of research by the Buck Institute for Research on Ageing and the University of Washington has identified 238 genes that, when silenced, increase the lifespan of yeast cells.

Many of the genes are present in mammals, including humans, suggesting that switching them off could dramatically increase lifespan.

“This study looks at aging in the context of the whole genome and gives us a more complete picture of what aging is,” said lead author Dr Brian Kennedy.

"Almost half of the genes we found that affect aging are conserved in mammals.

"Our best results were single gene deletions that increased lifespan by around 60 per cent compared to normal yeast."

Dr Mark McCormick, Buck Institute

"In theory, any of these factors could be therapeutic targets to extend healthspan. What we have to do now is figure out which ones are amenable to targeting.”

To determine which genes were responsible for ageing, researchers examined 4,698 strains of yeast, each with a single gene deletion and then monitored how long cells lived for before they stopped dividing.

They found that deleting a gene called LOS1 produced particularly impressive results, extending life by 60 per cent. LOS1 is linked to a genetic master switch which has long been associated with calorie restriction through fasting and increased lifespan.

"Calorie restriction has been known to extend lifespan for a long time," added Dr. Kennedy.

Co-author Dr Mark McCormick, of the Buck Institute said: "Our best results were single gene deletions that increased lifespan by around 60 per cent compared to normal yeast."

Earlier this year academics from the University of Southern California found that a five day diet which mimics fasting can slow down ageing, add years to life, boost the immune system and cut the risk of heart disease and cancer.

The plan restricts calories to between one third and a half of normal intake.

Last year the same team discovered that fasting can regenerate the entire immune system, bringing a host of long-term health benefits.

When humans tested out the regimen, within three months they had reduced biomarkers linked to ageing, diabetes, cancer and heart disease as well as cutting overall body fat.

The researchers think it works by slashing a hormone which encourages growth, and has been linked to cancer susceptibility. Essentially it tricks the body into ageing more slowly.

The new study was published in the journal Cell Metabolism.