Don't gain weight when you quit smoking.

A woman smokes a cigarette on January 17, 2014 in Times Square in New York City. Source: AFP 

SMOKERS may no longer be able to use getting fat as an excuse not to quit after researchers found weight gain is usually temporary. 

A study of about 1000 people in Dunedin also found those who quit probably don't put on as much weight as once thought.

Undertaken by the University of Otago and published in journal, Nicotine and Tobacco Research, the research studied people born in 1972-73 and measured smoking habits and weight at regular intervals.

The subjects were tested at ages between 15 and 38.

About one-third of the group were smokers at age 21 and about 40 per cent of those had quit by 38.

The study found quitters, both male and female, are likely to gain around five kilograms after giving up. However, their weight bounced back to similar levels of nonsmokers over time.

Smoking also does not prevent long-term weight gain, the study found.

"We hope that our findings will encourage people who are thinking about quitting. They should not be put off by the fear of putting on large amounts of weight," head researcher Lindsay Robertson said.

"It is important to be aware that a small weight gain is unlikely to offset the health benefits of quitting."

A new report from the Surgeon General shows the that list of negative side effects and diseases caused by cigarettes continues to grow, including diabetes, rheumatoid arthritis and erectile dysfunction.