Nicotine increases the metabolic rate. If you add an additional 20 minutes of cardio to your workout regime, you should be okay. I did this the "first" time I quit smoking and did not gain any weight. Of course, I picked it back up for a year, and now have quit again, so I'm going to try again. But the extra 20 minutes in cardio is supposed to make up for the difference the lack of nicotine will make with your metabolism. Good luck!!!