Scientists believe they are a step closer to working out why an extremely restrictive diet boosts longevity.
This well-documented calorie-cutting phenomenon has been seen in many species, from yeast to mice to dogs.
Although the effects of "calorie restriction" in humans are as yet unknown, some are undertaking this in a bid to live longer.
Here, Bob Cavanaugh, managing director of the Calorie Restriction Society, tells the BBC News website about his diet.
I've been doing calorie restriction for six years.
When I was 53, I had a physical and found out my blood cholesterol level was very high. My doctor wanted to try to control it with diet before resorting to drugs, and I was all in favour of that.
I had read a book about calorie restriction and ageing back in 1988, and was convinced by the science, so I decided to try it.
I use software to work out what to eat every day. I believe without it, it is impossible to have proper nutrition.Read more...
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