Low body temperature, low insulin and high levels of a specific hormone seem to be linked to a slowdown of the aging process.
It's now well known that calorie restriction increases the lifespan of animals. What's not clear is how this works. Now researchers at the National Institute of Aging have some new clues about slowing down the aging process. The compared a group of 700 healthy men, taking part in the Baltimore Longitudinal Study of Aging, with a group of rhesus monkeys. They followed the men for 25 years, the monkeys for 15.

The monkeys were in two groups - one following a normal diet, the other on calorie restriction. The latter tended to have a lower body temperature, lower blood insulin levels and higher levels of a hormone called dehydroepiandrosterone sulphate (DHEAS). These, say the researchers, could be the three biological markers of aging. The same profile was found in the men who lived longest - even though they were not practising calorie restriction. This suggests that you don't need to starve yourself to extend your lifespan. But more research is needed to find what factors (other than calorie restriction) influence the levels of the aging biomarkers.