The purpose of fasting is to deepen your relationship with God. It's a commitment to pray, meditate and praise ~ without any other distractions (including food). It's a time for you to focus solely on God and allow him to speak to you. It's a time to bath yourself in prayer.
Fasting is usually done before a huge decision or in order to intercede for others. It's taking you out of your comfort zone and allowing God to sustain you. Sometimes the whole Jewish nation would fast but most often it was (and still is) an individual thing. It's something to be boastful about to just relish God quietly. It can be for a day, several days or just one meal, but the purpose is to take the time you would normally do mundane things and substitute prayer in their place. It's a powerful thing.
at 11:02 AM on Nov. 13, 2008