Do you smoke?

Quitting smoking increases appetite, which leads to weight gain. This is not a trivial matter, especially for women!

Quitting smoking doesn't cause an increase in appetite; people simply decide to snack on something to keep themselves occupied (a couple of pastries, some candy). As a result, they gain excess weight, sometimes even becoming obese. :)
P.S. It has been scientifically proven that nicotine does not cause physical dependence (only psychological dependence).