It is all about burning more than you consume. The more you ride/run/whatever, the more you can consume. One of the reasons that I do so much exercise (other than liking it) is that I eat and drink anything I want. Just make sure to get some quality calories too.

Then you can laugh at people when they see you eating a cheeseburger and drinking heavy microbrews and say "you are so lucky to have a high metabolism..."

Just remember, you set your own metabolism.