It's a very simple my friend.
Burn more calories then you consume.
Do not quit smoking cause it will make you gain more wait. Diet is not as important as your eating habits. First eliminate simple sugars right away. And stop eating after 7 pm. You will loose alot of weight without going crazy at the gym. Simple walks will initiate the fat burning process. If you get on shakes and other supplements they are designed to give you added boost for workouts. Therefore stuff you with carbs. Unburned carbs turn into fat. And the circle continues . Good luck. Ps. Do not follow diets in the books and magazines. In order for those to be effective you have to do 45 cardio everyday and a full workout at least 3 times a week. It is possible to loose lots of weight without hitting the gym. Good luck.
Ps. It is very hard to a achieve your 80lbs loss. Make sure you set small goals and do not get discouraged. I have friends that compete and they do cardio for 3 hours a day. Now that's dedication. Good luck