According to them, the ‘ketogenic’ diet alters the body's metabolism by mimicking the effects of starvation and could be used as a substitute for epilepsy medicines, the Lancet Neurology journal reported.

In their study on 145 children aged between two and 16 who had failed to respond to medication, the researchers found the number of seizures fell by a third in those who were on the ‘ketogenic’ diet.

Though the number of seizures in the children on the diet fell to two-thirds of what they had been, but remained unchanged in those who had not yet started the diet.

Five kids in the diet group saw a seizure reduction of 90 per cent. However, the researchers found that there were some side-effects including constipation, vomiting, lack of energy and hunger.

According to study leader Prof Helen Cross of Great Ormond Street Hospital in London, the diet has been around for a long time but fell out of favour because it was thought to be too difficult to stick to.

"The parents say the first two weeks are quite difficult, but then it becomes much easier because you can make foods in bulk and it especially helps if you can see the benefits from it.

"We have to be sensible about it, in this study we had children who had complex epilepsy. If your epilepsy is easily controlled on one medication then I wouldn't advocate the diet, but if at least two drugs have failed then it should be considered," she said.

Experts in this field have welcomed the research but said that the side-effects should be considered before taking that diet.

"The results of this trial add valuable information to what is already known about the diet, presenting evidence that it works for some children with drug-resistant epilepsy.