Studies have shown that food intake, especially sweet foods and simple carbohydrates, generally increases after quitting. It takes a lot of energy to quit smoking, and the pleasure center of your brain may be looking for an effect previously provided by nicotine. The good news is that for most people, caloric intake returns to normal after their body adjusts to being quit.
(1) Abrams DB, et al. The tobacco Dependence Treatment Handbook: A Guide to Best Practice. 2003. pp18-19.