I'm a cigarette smoker and i want to quit.

2 things.
1. people who quit tend to gain, but gain less if they are exercising and actively trying to lose weight. You're in a great position right now to try to achieve *2 very difficult things at once*. But if you can't, who cares? Quitting itself is a fairly time limited experience. It will end. So if your goal is that you must do two very difficult things at once, fine, but if you end up not being able to perfectly quit smoking without gaining weight, just lose it when you're done. You'll be able to do that better because you'll be doing it as a nonsmoker. (I'm probably a minority opinion here, I know.)

2. I want to offer a suggestion of a quitting strategy that worked for me. Wake up in the morning and skip your first cigarette of the day. Do your morning routine, all the same, except without smoking. If you typically have a cigarette then get into the shower, just get into the shower. Then smoke the rest of the day normally. Do this for a few days. Learn to have coffee without a cigarette. It's weird but it gets better. Then wake up after 8 or so hours, skip your first cigarette that you would have and also skip the next one. repeat a few days. Now you're successfully moving from 8 hours a day of not smoking, to 9 to 10.5, etc. Don't smoke until your first break at work. then wait till lunch. then wait till after you get home from work. etc. It increases the time you're not smoking ever day and it also gets you into new nonsmoking habits around your daily routines.

Good luck with the process and remember that every time you quit, you get better at staying quit.