Nope, sorry, smokers can not gain. But hey! Good for you since you do not smoke anymore! I used to be addicted to nicotine, not through smoking but something we call snus here in Norway. It is kind of similar to chewing tobacco. Basically grind up tobacco with some added spice,salt and nicotine that you mold into a small ball and put under your lip. The nicotine is absorbed into the blood stream through the lip.
Anyway, I read a book and de-brain washed my self. I was basically finished with nicotine half through the book. I had just bought 100 units of snus in Sweden that I had in my fridge when I decided to quit. Sold it all.
The thing is, it really is quite easy when you know what you are doing. Nicotine gives almost zero abstinence symptoms so it is mostly in your head. The only abstinence one feel is a slight feeling of hunger. This passes within 3 weeks. If one manages to recognise this feeling, one can even quit without adding any weight like so many do.
(By the way, the first sentence of this post was a joke, I believe almost anyone can gain from PE.)