The New Scientist on calorie restriction: "Dreams of eternal youth feature in many cultures throughout history, but it was only in the 20th century that research into longevity really began. Much about ageing is still mysterious - we don't even know the underlying reasons why we journey into old age. There are many lines of enquiry into how to live longer, though, with one of the most intriguing being calorie restriction: in effect, going on a lifelong diet. Calorie restriction dramatically extends not only the lifespan of laboratory animals, but also their 'healthspan' - how long they live free of disease. On the assumption that it has the same effect in people, some individuals have already adopted a restricted diet. The latest evidence suggests that while calorie restriction is indeed beneficial for humans, when it comes to lifespan extension, it may not be the whole story. The good news is that we might be able to delay ageing without cutting our food intake. ... There's a definite possibility that if you balance the diet correctly, a longer lifespan can be achieved without full food restriction. ... It is unclear why eating less should make animals live longer. While a restricted diet triggers numerous changes at the molecular and genetic levels, only some of these are common across all the species tested. However, there does seem to be a general principle that a dearth of nutrients causes organisms to divert resources away from growth and reproduction and towards basic survival functions. From an evolutionary perspective, these adaptations could help an organism survive famine."