Cutting calories

Cutting calories may delay the ageing process and reduce the risk of disease, a long-term study of monkeys suggests.

The benefits of calorie restriction are well documented in animals, but now the results have been replicated in a close relative of man over a lengthy period.

Over 20 years, monkeys whose diets were not restricted were nearly three times more likely to have died than those whose calories were counted.

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Writing in Science, the US researchers hailed the "major effect" of the diet.
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It involved reducing calorie intake by 30% while maintaining nutrition and appeared to impact upon many forms of age-related disease seen in monkeys, including cancer, diabetes, cardiovascular disease and brain atrophy.

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Whether the same effects would be seen in humans is unclear, although anecdotal evidence so far suggests people on a long-term calorie-restricted diet have better cardiovascular health.

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The precise mechanism is yet to be established: theories involve changes in the body's metabolism or a reduction in the production of "free radical" chemicals which can cause damage.
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And here they are again

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Seventy-six rhesus monkeys were involved in the trial, which began in 1989 and was expanded in 1994.
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Half had their diets restricted, half were given free rein at feeding time.

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The rate of cancers and cardiovascular disease in dieting animals was less than half of those permitted to eat freely.

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While diabetes and problems with glucose regulation were common in monkeys who ate what they wanted, there were no cases in the calorie controlled group.

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People would have to weigh up whether they are prepared to compromise their enjoyment of food for the uncertain promise of a longer life

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Catherine CollinsBDA

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In addition, while most brains shrink with age, the restricted diet appeared to maintain the volume of the brain at least in some regions.

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In particular, the areas associated with movement and memory seemed to be better preserved.
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Both motor speed and mental speed slow down with ageing, said Sterling Johnson, a neuroscientist at the University of Wisconsin-Madison School of Medicine.

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Those are the areas which we found to be better preserved.

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We can't yet make the claim that a difference in diet is associated with functional change because those studies are still ongoing.

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What we know so far is that there are regional differences in brain mass that appear to be related to diet."

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Earlier this year, German researchers published findings from their study of elderly people which suggested that calorie reduction appeared to improve memory over a period of just three months.

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Various studies on the positive effects of calorie restriction on the life spans of various organisms - from yeast to dogs - have been published over the last 70 years

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But dieticians sounded a note of warning.

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Monkeys may be a close relation but there are significant differences which means not everything we see in them can be translated to humans," said Catherine Collins, spokeswoman for the British Dietetic Association.

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And there should be some serious reservations about cutting calories so dramatically, particularly for anyone under the age of 30.

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Any such diet would need to be very balanced to avoid malnutrition, and it would be a long-term commitment.

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People would have to weigh up whether they are prepared to compromise their enjoyment of food for the uncertain promise of a longer life, and a life which could be dogged by all sorts of problems - including osteoporosis."

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BBC