Losing and trimming down on belly fat is mostly(80%) to do with your diet as you already know. What you are looking to do is to decrease your carb intake slowly and increase your protein intake fast. If you cut carbs completely, your body will fight you and you will have trouble getting results. Recommended is 1-1.5 grams of protein per pound of body weight. This will help your metabolism speed up. Once it speeds up then your success rate will double. A great way to cut fat when working out is High Intensity Interval Training (HIIT) Read over this link to get a general idea. Its also great training for sport. If you need help with a meal plan and a workout guide then send me a pm.
http://en.wikipedia.org/wiki/High-in...erval_training