Smokers who quit are unlikely to gain as much weight as previously thought, a University of Otago study has found.
The study followed the progress of about 1000 people born in Dunedin in 1972-3 and measured their smoking habits and weight regularly from the age of 15 to 38.
About one-third of the group were smokers at age 21, and 40 per cent of those had quit by 38.
The study found both male and female quitters were likely to gain about 5 kilograms more than those who carried on smoking.
But over time, their weight returned to the same level as those who had never smoked.
Furthermore, being a smoker did not prevent long-term weight gain.
All groups put on weight as they aged, regardless of smoking status, the study found.
Head researcher Lindsay Robertson said earlier research had suggested people might gain large amounts of weight after quitting, but these studies were unreliable.
"It's a good message to be able to say, if you're thinking of starting smoking because of weight concerns, you're going to put on weight anyway," she said.
"The Government has a 2025 goal to become a smokefree nation, so to achieve that goal a lot of people have got to stop smoking."
It was helpful to identify barriers that could prevent people from quitting, she said.
"In this case the fear of putting on weight is not particularly valid, as on average most people won't gain a huge amount of weight."
The Dunedin Multidisciplinary Health and Development Study was supported by the Health Research Council New Zealand.
Findings were published in the Nicotine & Tobacco Research journal.
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