Fear of piling on pounds is a major stumbling block for many would-be ex-smokers.

But following a programme developed by doctors in Sweden, 50% of those quitting managed to stay off the cigarettes, compared to 35% who adhered to no particular regime.

However, there is some concern that the programme could prove too costly to implement and may only work for a limited group of women.

Special diet

Researchers at the Karolinska Hospital in Stockholm looked at 287 women over a 16-week period.

All of the women had tried quitting before, but had caved in over weight concerns.

One group was put on a special diet to keep their weight down and given nicotine gum, while the rest were just given the gum. Both sets attended group meetings for support.

Those on the diet saw their weight fall by an average of 2.1kg over 16 weeks and were more likely to stay off the cigarettes, while the others gained an average of 1.6kg and were more likely to start smoking again.

After a year the diet group were more likely to have stayed off the cigarettes, but there was no significant difference in weight between the two groups.

Publishing their results in the British Medical Journal, the researchers said: "Our study shows that smoking can be stopped for up to one year with acceptable weight control in a group of women selected for their previous weight control problems when attempting to give up smoking."

Difficulties in routine practice

However, commenting on the study Dr Kevin Jones of the School of Health Sciences at Newcastle Medical School, warned that the results were unlikely to be as good in routine practice.

"The first of these concerns is the nature of the sample of patients in this study," he said.

This would mean that patients wishing to take part in the programme would have to be carefully selected.

The intensity of the programme was another factor to consider, he said.

"Eleven, 45-minute group sessions - 10 to 15 women each - were held over 16 weeks," he said.

"This level of intervention is not only expensive but nearly impossible to provide in routine practice.

"Furthermore, the very low energy diet was provided free for the participants in this research - this would be unlikely outside the research setting."

Weight 'an important factor'

However, Clive Bates, director of Action on Smoking and Health, said health benefits of giving up smoking outweighed the cost of the programme - or indeed the harm of a little additional weight.

"Weight gain, in absolute health terms, is a mere blip compared to the health gain you would get from giving up smoking but it looms large in people's mind because they're concerned about their looks and how attractive they are," he said.

Nevertheless, it was important to tackle the weight gain issue because it played such an important role in people's motivation, especially when of the three to four million smokers who try to quit each year, only 300,000 to 400,000 succeeded.