It is the wrong 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. But the benefits are lost when the rats return to a normal diet.
Among humans, the Okinawan islands in Japan's extreme southwest are home to more than twice the national average of centenarians. As well as having a healthy diet, they have a 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 the 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, the sirtuins, which are linked to longevity.
While overeating ages the brain and can lead to Alzheimer's disease, calorie restriction increases the activity of Creb1, which regulates memory and learning.
Research in mice has shown that if they lack the molecule, the memory benefits 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 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."
DIET STYLES OF THE OLD AND HEALTHY
* Jeanne Calment, the oldest person in history, who died in 1997 aged 122, attributed her longevity to a diet rich in olive oil and 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 people to live, on average, to 83, thanks to its fat-absorbing qualities.
* Your parents make a difference - genetic inheritance plays the biggest part in living to a grand old age.