Yes, you do have to eat healthy to burn the fat off of your belly. You must have more calories going out and fewer calories coming in. There are 3,500 calories in one pound of fat, so you need to be eating 500 fewer calories (calorie negative) than what you burn daily (daily active metabolic rate) to lose one pound of fat a week.
If your daily active metabolic rate is 2,500 calories per day, then you should be eating 2,000 calories a day to burn off one pound. of fat in a week. You can use a metabolic calculator to calculate your daily active metabolic rate. Then subtract 500 and that will be the number of calories a day you should be eating so you can lose one pound of fat a week.