Huntington's is an incurable genetic disorder in which nerve cells in the brain are damaged, causing physical, mental and emotional changes.

It usually starts when people are aged between 30 and 50.

The US research suggests that changing diet can influence the course of the disease.

I wouldn't like it to be said that looking at restricting diet would be something that could be a research avenue Sue Watkin Huntington's Disease Association

The team from the National Institute on Aging genetically created Huntington's symptoms in mice.

They developed signs of the disease, including a diabetes-like metabolism problem, which meant the mice lost weight even though they ate well.

They later lost control of their body movements and eventually died.

Post-mortem examinations of their brains showed nerve cells in the striatum, a brain region that normally helps control body movements, had degenerated, as happens in humans with Huntington's.

Living longer

But the post-mortems showed that those mice which were starved on some days and given low-calorie diets the rest of the time developed signs of the disease around 12 days later than those allowed to eat as much as they wanted.

They also lived 10%-15% longer, were better able to regulate their glucose levels and did not lose body weight as quickly as the other mice.

Their brains had fewer affected nerve cells, and higher levels of a growth factor for nerve cells called BDNF (brain-derived neurotrophic factor).

BDNF stimulates the growth and survival of nerve cells.

The researchers suggest that fasting may increase levels, and therefore protect nerve cells from the adverse effects of the mutant Huntington's gene.

Good diets

Dr Mark Mattson, head of the NIA's Laboratory of Neurosciences, who led the research said BDNF may help regulate energy metabolism.

Other studies have shown that mice with a genetic deficiency in BDNF are diabetic and that increasing BDNF levels in the brain improves glucose regulation in these mice.

But more research is needed to see if the problems with glucose metabolism in Huntington's are also linked to BDNF.

Dr Mattson said: "We're exploring the idea that increasing the levels of BDNF in the brain can forestall Huntington's disease without a change in diet."

Sue Watkin, chair of the UK's Huntington's Disease Association, said: "Looking at BDNF levels could be helpful."

But she said: "So far, people have always said that you should have as good a diet as possible.

"Anecdotal evidence from clinicians who observed who were poorly fed do less well.

"I wouldn't like it to be said that looking at restricting diet would be something that could be a research avenue."

The research is published in the online version of the Proceedings of the National Academy of Sciences.