Portion control and diet is the key though, u can chew as much as you like but if its a large portion of fish and chips then you will still put on weight. Idealy you should have 2/4 veg, 1/4 lean meat (palm sized) 1/4 carbs on your plate and do as much excercise as possible (at least 30 mins per day), and no carbs after tea time. Try to eat 6 x per day, 3 main meals and 3 healthy snacks to keep your metabolism high.
Also my grandad stopped smoking after 45 years and did it by substituting fags for chewing gum, stock up on sugar free chewing gum and stuff your face with this when you get a craving.
Good luck, its hard work but you will feel so much better for it.
R