Another mince pie? Scientists find the secret to a long, indulgent life

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It is a challenging time of year to be told that eating less is good for you but evidence has for a long time suggested that cutting down on calories extends life.

Now Italian researchers have identified a molecule produced when people diet that could lead to the development of a drug that mimics the effect of restraint, offering a longer life without the need for self-denial.

Experiments have shown that curbing the amount of food rats eat can extend their lives by 25 to 40 per cent. However, anti-ageing benefits are lost when the rats return to a normal diet.

Among humans, the population of the tropical Okinawan islands in Japan's extreme south-west are home to more than twice the national average of centenarians. As well as having a healthy diet, their longevity is attributed to their cultural habit of calorie control called hara hachi bu – or "eat until you are 80 per cent full".

Italian scientists from the Catholic University of Sacred Heart in Rome have now come a step closer to understanding how dieting works. It causes the body to activate a molecule called Creb1 which in turn activates another set of molecules linked to longevity called the sirtuins.

While overeating ages the brain and can lead to Alzheimer's disease, calorie restriction increases the activity of Creb1 which is known to regulate memory and learning. Research in mice has shown that if they lack the molecule, the benefits in terms of improved memory from cutting down calorie intake are not seen.

Giovambattista Pani, who led the study published in Proceedings of the National Academy of Sciences, said: "Our findings identify for the first time an important mediator for the effects of diet on the brain. Our hope is to find a way to activate Creb1, for example through new drugs, to keep the brain young without the need for a strict diet." Biologists believe that restricting calories causes animals to go into a state normally reserved for near starvation.

Instead of spending their energy reserves on reproduction, they shut down everything but their basic body maintenance, in preparation for a future time when breeding would stand a better chance of success.

Self-preservation: how to stay healthy

* Jeanne Calment, the oldest person in history, who died in 1997 aged 122, attributed her longevity to a diet rich in olive oil, port and "regular smiling".

* Cleopatra, queen of ancient Egypt, took baths of asses' milk to preserve the beauty and youth of her skin.

* In 18th-century France, noblemen were obsessed with the quest for longevity. Some believed that if you found a magic formula it should be stored inside a clock, literally to hold back time.

* Seaweed-eating nations often have higher-than-average life expectancies. In Iceland dried seaweed known as sol is credited with helping nationals to live, on average, to 83, thanks to its fat-absorbing qualities.

* Your parents make a difference if you want to live to a grand age – genetic inheritance plays the most important part.