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A MEAGRE diet may give you health and long life, but it’s not much
fun—and it might not even be necessary. We may be able to hang on to most
of that youthful vigour even if we don’t 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’s 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’t reverse other ravages of time for the
mouse, but could help its liver metabolise drugs or get rid of toxins.

Spindler’s 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—equivalent 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—presumably 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.

“This is the first indication that these effects kick in pretty quickly,”
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. “There’s tantalising evidence out there that it will
work,” 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’t sure the trade-off is worth it. “[The mice] get less
disease, they live longer, but they’re hungry,” he says. “Even seeing what a
diet does, it’s still hard to go to a restaurant and say: ‘I can only eat half
of that’.”

Spindler hopes we soon won’t need to diet at all. His company, LifeSpan
Genetics in California, is looking for drugs to mimic the effects of calorie
restriction.