New research has found that ex-smokers put on more weight than once thought, with the average weight people can expect to put on now standing at 5kg (11lb) within a year of quitting.

Research published on bmj.com has found that people put on an average of 5kg (11lb) within a year of quitting smoking, which is far more than the 3kg often quoted in advice leaflets. It is also considerably more than the 2.3kg many women smokers say they are prepared to put on in order to quit the habit.

However, health experts have noted that the modest weight gains still far outweigh the benefits of giving up smoking. Many people continue to smoke because they are afraid of piling on the pounds, but the study also demonstrated that the changes in body weight varied widely from person to person, which shows that weight gain is not an inevitability.

The research collaborated results from 62 studies, finding that former smokers gained an average of 4.67kg in the 12 months after they quit. However, 16 per cent of quitters lost weight, while 13 per cent gained more than 10kg, which shows that there is certainly a lot of variation from one person to another.

Additionally, even though weight gain of ex-smokers exceeds that of ‘never-smokers’, after a few years the rate of weight gain falls to that seen in people who have never smoked.

Professor Esteve Fernandez, of the University of Barcelona, and Professor Simon Chapman, of the University of Sydney conclude in their editorial notes: “Although obesity is positively associated with an increased risk of all cause mortality, cohort studies indicate that modest weight gain does not increase the risk of death – smoking does.”

A Department of Health spokeswoman said: “The health benefits of quitting are well recognised. Each year smoking accounts for over 100,000 deaths in the UK and one in two long-term smokers will die prematurely from a smoking-related disease.

“Getting support from nicotine replacement therapies or medication and the NHS Smokefree service can help in keeping down your weight.”