That is easy to say but as an ex smoker you find yourself eating to take the place of the smoking-I think it's very natural when you first quit. That said, the weight gain (if kept to 20 lbs or so) is still not as unhealthy as the smoking. I found that my metabolism did 'correct' itself somewhat after I stopped smoking but I did have to work at losing 15 lbs about 6-8 months after quitting smoking.
I have seen the Sensa ads too and have been intrigued because now I have 10-15 lbs extra from my over 45 (almost 50) spread. No matter what I do I am finding this weight very hard to drop no matter what I do.