having watched most (as in every member) of my family gain considerably more than a 'few extra pounds' in weight quitting smoking, whilst I agree the health benefits are good, I can also tell you that several of them are now suffering from other weight related health problems related to gaining those few extra pounds and in the case of my mother, it severely affects her life, has done all of her life and is going to make her old(er) age much more difficult, to the point where it has meant she has had to change her house because of those health issues. I have seen my mother say she can exercise it off, she can diet it off, and seen her fail time and time again, pretty much all of my life. With my brother, he has had to give up hobbies that were important to him (motorcycling) and change his job (he was a motorbike courier). With my sister it is constant dieting also, but also gym 5 times a week before work - she is burning herself out and is on the way to a nervous breakdown and has numerous medical issues, some as yet undiagnosed and all related to trying to loose the weight after quitting smoking. Only my younger brother has yet to quit smoking, his father still does as well, but has tried repeatedly, put weight on and never lost it. My younger brother is 26.
All I am saying is don't fall for the snacking on fruit is healthy and low calorie. It is not always as low calorie or healthy as people believe.
Informed decisions early on will help as will watching your weight as you quit.
Best of luck