Louisiana: The first calorie-controlled diet to extend life in humans has confirmed that it reduces signs of ageing.

Researchers at Louisiana State University found that six months on a low calorie diet was enough to significantly cut the chances of developing diseases of ageing such as cancer. The findings are published in the current issue of the Journal of the American Medical Association.

A group of 48 overweight men and women aged between 25 and 50 were monitored in the experiement over a six month period.

A quarter of them were put on a diet of 25 per cent fewer calories than they would be expected to eat for their age and weight.

Another quarter had their calorie intake reduced by 12.5 per cent and were also put on a strict exercise regime.

A third group stuck to a very strict diet of 890 calories a day – which compares with guidelines for people with low activity levels of 1,640 calories for women and 2,550 for men. The remainder were placed on a regime designed to maintain their weight.

The volunteers on the fewest calories lost 14 per cent of their body weight on average over the six months, while the other calorie-restricted dieters both lost 10 per cent.

All of those who cut down on their calories showed a fall in average core body temperature and reduced fasting insulin levels, both linked to living longer.

The rate at which their DNA decayed – a natural process – also slowed, reducing their chances of developing mutations and degenerative diseases related to ageing such as cancer.

Earlier this year scientists at Washington University also discovered that people on calorie-controlled diets had more elastic than others of the same age and gender.

After an average of six years on the regime, the experiment established that their hearts were able to relax between beats in a manner associated with much younger people.

Dr Luigi Fontana, who led the Washington study, said the latest research was the first to show a significant decline in DNA damage from calorie restriction.

He said: ‘The value of these studies is that they suggest possible mechanisms of ageing in humans and points of intervention to modify the effects of ageing.’

Dr Fontana’s colleague, John Holloszy, who originally found caloric restriction increased lifespan in mice and rats by 30 per cent, said the research was a turning point.

He said: ‘It’s becoming clear from studies that calorie restriction does change some of the markers we associate with ageing.’

Doctors Fontana and Holloszy will soon begin a study into the effects of a calorie-restricted diet over two years.

‘We know people on calorie restriction will lose weight,’ Dr Fontana said. ‘But this study isn’t a weightloss study. We’re hoping to learn more about whether calorie restriction can alter the ageing process.’

In long-term studies on monkeys carried out by the U.S. National Institutes of Health, those on calorie- controlled diets suffered fewer ailments such as cancer, cardiovascular disease and diabetes.

One of the underfed monkeys reached 38 years, the human equivalent of 114 years.

Experts believe cutting calories works by causing biochemical changes in the body, reducing free radicals, the toxic particles created by the breakdown of food which are more difficult to eradicate in an ageing body.