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Posted on Jun 02, 2005, 7 a.m.
By Bill Freeman
The idea that animals live longer if they eat less has been shown to be not entirely correct - at least in fruit flies. For these insects, it is the type of food and not just the quantity that controls their longevity. It has been known for some time that
It has been known for some time that “calorie restriction” significantly lengthens the lifespan of many non-primate species - everything from worms to fleas to mice. Linda Partridge at University College London, UK, and colleagues wanted to see if the effect was merely due to a reduction of total calories or of particular nutrients in the diet.
So the researchers divided up their Drosophila melanogaster fruit flies into four groups and put them on different diets. The control group got the standard fruit fly lab meal of yeast, which contains protein and fat, and sugar - a meal boasting about 1200 kilocalories per litre.
The second group was fed on a calorie-restricted diet, with equal amounts of yeast and sugar - about 521 kilocalories per litre. The third group was given more yeast than sugar, while the fourth group got more sugar than yeast. The latter two diets had about 860 kilocalories per litre each.
Choice meal
The flies on the calorie restricted diet lived the longest - 82% longer compared to the controls. But the flies on the higher calorie diet with reduced yeast intake did very well too.
Lowering the amount of protein and fat in the flies’ diet helped increase lifespan by nearly 65%. “It accounts for nearly all of the effect,” says Partridge. “It cannot just be calories.” Eating less sugar increased longevity only by about 9%.
Brian Kennedy, a researcher who works on calorie restriction and ageing at the University of Washington in Seattle, US, says: “It's these detailed studies that are going to unlock the secrets [of the effects of calorie restriction].”
Journal reference: PLoS Biology (vol 3, p e223)
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