A pill which may “lock in” the benefits of dieting, allowing dieters to return to normal eating without putting on weight, has been discovered by scientists.

The inventors also claim that the pill, a dietary supplement called
alpha-lipoic acid and widely sold in health food shops, also slows ageing,
which is a known effect of low-calorie diets.

But the finding has triggered a dispute between two of the scientists who
carried out the research, conducted in rats, over whether it can be applied
to humans.

Malcolm Goyns, director of Immorgene Concepts, a UK-based scientific
research company, who led the research, said he was sufficiently convinced
to follow the approach himself.

Evidence from the tropical Okinawan islands in Japan‘s extreme south-west,
which has the highest proportion of centenarians in the world, demonstrated
the life-prolonging effects of calorie restriction, he said.

Their traditional diet is high in vegetables and fish and low in fat, but
they also have a cultural habit known as hara hachi bu – or “eat until you
are 80 per cent full”.

This is based on the notion that it takes the stomach’s stretch receptors 20
minutes to tell the brain how full it really is, preventing overeating – and
Okinawans are among the leanest and fittest people in Japan as a result.

Dr Goyns said: “While calorie restriction diets are followed as a matter of
course in communities like Okinawa, the diet can be difficult to follow for
most people. Our discovery indicates that by following a calorie restriction
diet for six months and then taking alpha-lipoic acid while eating normally,
the same life extension effects will be experienced.”

He added: “Simply adding the supplement to the diet has no effect. It seems
that alpha-lipoic acid fools the body into behaving as if it was still on
whatever diet it was following before the supplement was added. We found
there was an anti-obesity effect as well. Although weight does rise when you
come off the restricted diet, if you take alpha-lipoic acid, even though you
are eating normally again you still have a reduced weight.”

The study, published in Mechanisms of Ageing and Development, was carried
out by Dr Goyns with colleagues from the University of Liverpool. The
researchers investigated the effect of alpha-lipoic acid when given to rats
on normal and low calorie diets.

Experiments have shown that curbing the amount of food rats eat can extend
their lives by 25 to 40 per cent. However, anti-ageing benefits are lost
when the rats return to a normal diet. In the study, researchers found the
benefits of the low calorie diet were extended by giving the rats the
supplement when they returned to normal eating.

Brian Merry of the School of Biological Sciences at the University of
Liverpool, who carried out the study, said: “If you put the animals on to a
restricted diet they would normally go on to an extended survival
trajectory. When they were switched to a normal diet, this compound seemed
to lock them into the benefits of their pre-existing diet.”

“It is an unusual and interesting finding and it needs repeating in further
research. That was as far as I was prepared to go, but Malcolm [Goyns]
wanted to apply it to humans. I said I didn’t agree with his interpretation
and we had to wait for further studies.”

He added: “People have been buying this stuff and taking it for years as a
dietary supplement. I don’t think anyone knows what its effect is. There
have only been two studies in rats and mice [before our study].

“It is also sometimes used in stroke patients to treat re-perfusion injury.
What happens as the blood supply is restored after a stroke is oxidative
damage to the cells. Alpha-lipoic acid is an antioxidant and can help reduce
the damage. It is also used to treat diabetics and oxidative damage to the
liver in people who have eaten poisoned mushrooms.”

Alpha-lipoic acid is sold as an anti-oxidant supplement and is also used in
the treatment of certain conditions including stroke and liver damage.