Weight was never an issue for me until after I quit smoking the year I turned 40. It's never too late to quit smoking, but I would suggest doing it earlier as opposed to later, for many reasons.
It probably didn't help that we (my husband quit at the same time as I did) rewarded ourselves with pie a lot. We would say "we haven't had a cigarette in X number of days, so let's go get some pie", and off we would go to the store to buy pie and ice cream, or cheesecake, or whatever sweet treat that caught our eye. We didn't just get a piece, we would get a whole pie, or cake.