Fit FAQ has an article that notes that speeding up your workout and adding intensity helps you lose belly fat faster:

Wanna lose belly fat, get healthier, and look better for spring? Then speed up your workouts! A recent study from Duke University found that people who perform regular higher-intensity workouts were able to significantly lower their abdominal fat levels and lose weight relatively quickly.


However, people who only did low-intensity exercise (like walking at an easy pace) for 30 minutes per day, 5 days a week did not lose any belly fat — in fact they gained an average of 1 1/2 pounds over the course of the 8-month study!