Is it harder to lose weight after you quit smoking?

I quit smoking four months ago, and have gained quite a bit of weight. I know I eat too much and I’m sure it’s because I am substituting smoking with food. Anyway, I worked out and dieted hardcore for over a month and nothing happened. Normally I lose weight relatively quickly if I am working my butt off at the gym and watching my diet. Is this lack of weight loss due to my quitting smoking? I smoked for 9 years.