the reason why ex-smokers gain weight comes from a combination of things. first, you have the lack of nicotine. nicotine is a stimulant. it not only speeds up the body, but it surpresses appetite. then youve got the lack of hand-to-mouth. the ex-smoker replaces that with food. and finally, you have the increased taste stemming from the lack of tar on the tongue dulling the taste buds. so food is not only satisfying the hand-to-mouth tendancy, its also tasting much better. further, you dont have that stimulant to curb appetite, or help you burn the food off.