weight training is a good thing to do if you get the proper coaching on how to get started. but probably what will help you most with the belly fat is Long, Slow, Distance rides.

moderate exercise that extends for 40 minutes or greater causes your body to release a hormone that, in turn, helps you tap into fat as a primary energy source. if your workouts are aerobic (like with interval training) your body will preferentially use the glycogen stores in your muscle and blood stream as an energy source.

my favorite nutrition author, Monique Ryan, has a book on nutrition for athletes that talks about this kind of stuff in a really accessible way.