A 20-year study found cutting kilojoules by almost a third slowed
the ageing of monkeys and fended off death.
This is not about a quick diet to shed a few kilograms.
Scientists have long known they could increase the lifespan of mice
and more primitive creatures - worms, flies - with deep, long-term
cuts in what should be normal consumption.
Now comes the first evidence that it delays the diseases of
ageing in primates, too - rhesus monkeys living at the Wisconsin
National Primate Centre. Researchers reported their study in
the journal Science.
What about those other primates, humans? Nobody knows yet if
people in a world better known for overeating could stand the
deprivation long enough to make a difference, much less how it
would affect our more complex bodies. Still, small attempts to tell
are under way.
Less disease in kilojoule-restricted monkeys
"What we would really like is not so much that people should
live longer but that people should live healthier," said Dr David
Finkelstein of the National Institute on Ageing. The Wisconsin
monkeys seemed to do both.
"The fact that there's less disease in these animals is
striking," Finkelstein said.
The tantalising possibilities of kilojoule restriction date back
to rodent studies in the 1930s. But it is a hot topic today among
researchers trying to understand the different processes that make
our bodies break down with age, so maybe some of them could be
delayed or reversed.
Captive rhesus monkeys have an average lifespan of 27 years, so
spotting an effect takes a lot longer than in short-lived mice. The
newest study involves 76 monkeys - 30 tracked since 1989 and 46
since 1994. They were normal-sized adults eating a normal diet for
a captive monkey, a special vitamin-enriched chow plus some fruit
Then researchers at the University of Wisconsin, Madison,
assigned half the monkeys to the reduced-kilojoule diet, cutting
their daily kilojoules by 30%, but ensuring what they did eat
was properly nourishing.
What the study found
So far, 37% of the monkeys who kept their regular diet
have died of age-related diseases - compared with just 13% of the kilojoule cut monkeys, a nearly three-fold difference, the researchers reported. A handful of other monkeys died of unrelated conditions, such as injury, not deemed affected by nutrition.
Death was not the only change. The calorie-cut monkeys had less
than half the incidence of cancerous tumours or heart disease as the
monkeys who ate normally. Brain scans showed less age-related
shrinkage in the dieting monkeys. They also retained more muscle,
something else that tends to waste with age.
Compare two cage-by-cage photos of the monkeys and the
difference is obvious: A 29-year-old monkey happens to be the
oldest non-dieting monkey still alive, and a 27-year-old the oldest
still-living dieter. Yet the dieting monkey looks many more years
younger than his fatter, frumpier neighbour, not just a mere two.
"All these pieces put together provide rather convincing
evidence in our view that caloric restriction can slow the aging
process in a primate species," said lead researcher Dr Richard
Weindruch, a University of Wisconsin professor heading the
’Follow common-sense healthy lifestyle’
He contends that somehow the diet change is reprogramming
metabolism in a way that slows aging.
The federal government is funding a small study to see if some
healthy normal-weight people could sustain a 25% kilojoule cut
for two years and if doing so signals some changes that might, over
a long enough time, reduce some age-related disease.
But NIA's Finkelstein cautions that people should not just try
this on their own; cutting out the wrong nutrients could cause more
harm than good. Just follow commonsense healthy lifestyle advice,
"Everyone's obviously looking for the magic pill," and there's
not one, Finkelstein said. "Watch what you eat, keep your mind
active, exercise and don't get run over by a car." – (Sapa, July 2009)
Low kilojoule diet works best