Quitting smoking for me was the path to gaining weight. I found myself 20 pounds heavier after a month or two. I basically switch from smoking to over eating. I managed to lose it again, though.
I went the opposite way. Accustomed to lighting after even so much as a glass of water, lingering over a meal made me want to smoke so much, I had to leave the table the moment I finished eating. The smoking was stopped and the lingering never reinstated.