The only way you will lose fat is if you burn more calories in the day than you consume. This means that people usually need to reduce calories AS WELL AS do exercise in order to see results. You might see slow results if you were to run without reducing your calories, but this would only happen if you are currently not consuming more than you need.
Basically, it's best to work out how many calories you are consuming on an average day, and do the various calculations involving your weight to work out how many calories you need to drop in order to shed fat.
You mention that your goals are to lose the fat around your belly. This is ok as long as you understand that the fat will be reduced all over your body and not just targetted at your belly.