How to decrease belly fat while cycling?
You cannot outride (or outrun or out-any-other-exercise) a bad diet. On top of that, decades of research shows it's impossible to "spot-reduce".

Your options are:


Eat some combination of food that results in fewer calories in. Shoot for somewhere between 200-500 fewer calories for moderate weight loss.
Ride some combination of harder and longer while maintaining your current intake. Harder could be adding hill climbs and sprint intervals. Longer would be adding a 3-4 hour ride on the weekend or something. This is hard to because as soon as you start riding harder you will want to eat more. It takes strong self discipline. It also assumes your diet isn't horrible to begin with.
Do a combination of the first two.
Forget everything above and start saving for liposuction or any of the other modern body sculpting surgeries. Personally I'd rather spend that money on a nicer bike and continue to try to ride the belly off, but to each their own.


Outside general weight/fat loss, strength and endurance exercises targeting the area will tone the underlying muscles, but will have little to no effect on your spare tire.