Some of the comments on a different thread makes me think that many don't think fasting is desired of us by God. Why do you think He said in Mat 6:16 'When' you fast, not 'if' you fast?
Many commentaries take Mat 5,6 and 7 to be the sermon of the lifestyle Jesus intended us to live, of fastingwithprayer, giving, serving, forgiving, etc. as the highest expression of our devotion, and at the end He says anyone who teaches other than this will be called least in the Kingdom of heaven.
Mat 9:15 How can the friends of the Bridegroom fast when He is with them? but the days are coming when He will be taken from them, and then they will fast. Then they will fast seems to mean fasting will be a part of their lifestyle, because like the wise virgins of Matt 25, they have oil in their lamps, and also in vessels, they can't get enough oil, they can't get enough of the Holy Spirit, because they have a revelation of the returning bridegroom. Both of these NT revelations of the Bridegroom deal with hunger for God. The foolish virgins only get enough of the Holy Spirit to get through the day, bare minimum and mostly desire other things for fulfillment.
This fasting is to get more of God, get closer to Him and experience His presence more, hear His voice clearer. I think it is the very essentials of Christianity. The gospel in the west is kind of Americanized for our cultural lifestyle but Jesus seemed to be speaking something deeper than just fasting in crisis or for direction, once every five years.
For the healthy, it is fasting food, to be weak in the body is to have strength in the Spirit to experience God (2Cor12:9). Not that you have to fast to experience God, but that you want more. Fasting increases our capacity to experience the Holy Spirit and receive from God, revelation and affection and His presence. Blessed are the hungry for they will be filled. (Luk 6:21)
Do not be drunk on wine, instead be filled with the Spirit (Eph 5:18)
You will seek Me and find Me when you seek with all of Your heart. (Jer 29:13)
I pray you be strengthened with might in your inner man... that you may be filled with the fullness of God (Eph 3:16-19)