杏吧原创

A MEAGRE diet may give you health and long life, but it鈥檚 not much
fun鈥攁nd it might not even be necessary. We may be able to hang on to most
of that youthful vigour even if we don鈥檛 start to diet until old age.

Stephen Spindler and his colleagues from the University of California at
Riverside have found that some of an elderly mouse鈥檚 liver genes can be made to
behave as they did when the mouse was young simply by restricting its food for
four weeks. The genetic rejuvenation won鈥檛 reverse other ravages of time for the
mouse, but could help its liver metabolise drugs or get rid of toxins.

Spindler鈥檚 team fed three mice a normal diet for their whole lives, and fed
another three on half-rations. Three more mice were switched from the normal
diet to half-feed for a month when they were 34 months old鈥攅quivalent to
about 70 human years.

The researchers checked the activity of 11,000 genes from the mouse livers,
and found that 46 changed with age in the normally fed mice. The changes were
associated with things like inflammation and free radical
production鈥攑resumably bad news for mouse health. In the mice that had
dieted all their lives, 27 of those 46 genes continued to behave like young
genes. But the most surprising finding was that the mice that only started
dieting in old age also benefited from 70 per cent of these gene changes.

鈥淭his is the first indication that these effects kick in pretty quickly,鈥�
says Huber Warner from the National Institute on Aging near Washington DC.

No one yet knows if calorie restriction works in people as it does in mice,
but Spindler is hopeful. 鈥淭here鈥檚 tantalising evidence out there that it will
work,鈥� he says.

If it does work in people, there might be good reasons for rejuvenating the
liver. As we get older, our bodies are less efficient at metabolising drugs, for
example. A brief stint of dieting, says Spindler, could be enough to make sure a
drug is effective.

But Spindler isn鈥檛 sure the trade-off is worth it. 鈥淸The mice] get less
disease, they live longer, but they鈥檙e hungry,鈥� he says. 鈥淓ven seeing what a
diet does, it鈥檚 still hard to go to a restaurant and say: 鈥業 can only eat half
of that鈥�.鈥�

Spindler hopes we soon won鈥檛 need to diet at all. His company, LifeSpan
Genetics in California, is looking for drugs to mimic the effects of calorie
restriction.