Heavy smokers gain more weight when they quit tobacco — up to 23 pounds on average.

That’s the upshot of new research at Penn State College of Medicine that finds weight gain in reformed smokers can range from a few pounds to more than 25, depending on how much they smoke and their weight before quitting.

"Many smokers are concerned about gaining weight after quitting smoking and this can be a barrier for them when they are considering whether or not to make a quit attempt," said Susan Veldheer, a registered dietitian in the Department of Public Health Sciences, Penn State College of Medicine. "Being able to easily identify smokers who may gain more weight when they quit is important so that we can work with patients to tailor their treatment plan."

For the new study, reported in the International Journal of Obesity, the researchers analyzed data from 12,204 participants in the long-running National Health and Nutrition Examination Survey. They tracked the number of cigarettes smoked per day and body mass index before quitting, to see how these factors affected weight change over 10 years.

The results those who smoked fewer than 15 cigarettes per day before quitting gained the least weight, but those who smoked more 25 cigarettes per day gained an average 23 pounds. In addition, obese smokers reported 16 pounds of weight gain that could be directly attributed to quitting.

"Although this may seem like a lot of weight, it is important for all smokers to remember that quitting smoking is the single most important thing they can do for their health," said Veldheer. "That being said, for heavy smokers and obese smokers, it may be a good idea to work on quitting smoking while also making other healthy lifestyle changes to control their weight."