i know that typically, the bible says that fasting is about not eating. but it does mention that the fast that God likes best is that in which people "fast" from doing wickedness (Isaiah 58:6). so, extending that a bit metaphorically, it is perhaps a type of "fast" to avoid certain activities and habitual actions that can inhibit us spiritually and that can perhaps clog our spiritual arteries. and along that line of thought, here is a short little vid i created about fasting and prayer that you may find encouraging (or challenging): improve your prayer life...KILL YOUR TV! - YouTube