Welcome to HCM! I can help you with your problem, I just wish you had asked BEFORE you quit smoking. When my patients make up their minds finally to quit smoking, I guide them on a weight loss/calorie controlled diet (even if they don't need it at the time). Most smokers gain 20 lbs when they quit because of a shift in the enzyme lipoprotein lipase. So, in order to avoid the weight gain, add thermogenic aids, cut down on calories and exercise to avoid that unavoidable fight with your metabolism.
To lose the belly fat cut down on carbohydrates and do crunches every day. Visit my fitness board at https://www.pinterest.com/kathyshattler/ for sample exercises.
Good luck and don't give up! Kathryn Shattler, MS,RDN

Welcome to HCM,
When one quits smoking there is a biological change in the levels of lipoprotein lipase causing you to gain weight despite no change in caloric intake. When an individual quits smoking they should lower their calories at the same time to avoid the typical 20 pound weight gain accompanying the smoking cessation.

Of course there is still the craving to put something in one's mouth, so I generally suggest chewing on gum, cinnamon sticks, mints. Have a list of low calorie snacks planned out ahead of time and keep the pantry stocked with more acceptable "oral" fixes.

Your body will be particularly sensitive to storing fat, so stay away from it. It has been five months and your body should have stabilized by now. Perhaps you haven't gotten used to the fact that you cannot eat as much as when you were a smoker.

It is important to get rid of the belly fat you have accumulated as research now calls it "sick fat" due to its metabolic activity. In such a case, if you were my patient, I would reduce your calories to around 1500, restructure my exercise program to include cardio exercises at 70% maximum heart rate (220 - age = maximum heart rate x .70 = target heart rate) and maintain that for a minimum of 20 minutes ( remember warm up and cool down).

Eat 20% of your 1500 calories as protein or .2x1500 = 300 kcal/4kcal per gm = 75 grams of lean protein of which some protein should always be included at breakfast. Fat should be no higher than 50 grams per day leaving 188 grams of carbohydrate to spread evenly throughout the day.

Once the belly fat is gone, your system should be re-balanced. Just continue to eat healthfully, exercise regularly and you can start gradually increasing your calories to maintenance level. I cannot tell you what that would be without age, height, weight.

Does this give you some direction? Kathryn Shattler, MS,RDN