The answer to cycling or running for belly fat will depend on which one you enjoy doing more. Both running and cycling help burn calories, improve heart health, and you can practice them as indoor and outdoor exercises. In general, you burn a similar number of calories when you run or cycle. However, as with all physical activity, the actual calories your burn will depend on the workout's intensity and duration. So to increase the number of calories you burn, you can either increase your speed, add hills or try interval training, changing between periods of speed and recovery periods.