Q: I’m 39 and was a smoker for 25 years. I quit 10 months ago and ended up gaining 35 pounds, ballooning from a Size 6 to a Size 12. I have now started exercising and following a healthier diet. What kind of changes does the body go through that have contributed to my rapid weight gain, and what can I do about it?

A: Congratulations on giving up ciggies—and sticking to it!

A large percentage of quitters, especially women, will relapse. The theory is that post-cessation weight gain is one reason they are driven back to the bad habit. And it appears that, on average, a little weight gain after quitting is to be expected. What’s unclear is exactly why that happens, but research shows a small increase in areas such as body mass index, body fat and weight.

Many researchers have found that concern over gaining weight is one reason many smokers don’t even try to quit. Yet one study reported in the scientific journal Addictive Behaviors found the average weight gain tends to be much less than potential quitters fear—research shows that on average people gain around 6 to 9 pounds.

Of course, the general nonsmoking population tends to gain weight over time. too. Smokers  somehow may better able to control the pound-or-so per year that most people gain—and if they quit, they just slide back into the trend of the general population.

Why might smokers have an edge when it comes to weight control? Smoking may act as an appetite suppressant, making it easier to consume less food than nonsmokers. (Many women, most notoriously professional dancers and fashion models, anecdotally report smoking for just this reason.)

Plus, nicotine activates the adrenergic nervous system, resulting in a slightly speedier metabolism—this may help keep weight gain in check. Of course, the many nasty side effects that come with the package make using smoking to control body weight a bad idea.

You seem to have gained more weight than average, and it’s good that you’re now trying to address it with better eating and more activity. The reason most of the population gradually gains weight is precisely because they fall into an unhealthy lifestyle: Smoking or not, they still may be on a self-destructive path eating too much junk food, too many calories and being too inactive.

The solution for quitters and nonsmokers alike is to move frequently and eat better. The more you exercise—ideally working up to a point where you are fitting in 60 to 90 minutes per day of activity such as walking—the leaner you’re likely to be.

Eating often can be a substitute activity for smoking, so in addition to eating more healthfully it’s a good idea to find substitute behaviors that don’t involve food for those times when you’re trying to distract yourself from a cigarette craving.