What is Fasting?
A biblical definition of fasting is a Christian’s voluntary abstinence from food for spiritual purposes. It is Christian, for fasting by a nonChristian obtains no eternal value because the Discipline’s motives and purposes are to be God-centered. It is voluntary in that fasting is not to be coerced. Fasting is more than jus the ultimate crash diet for the body; it is abstinence from food for spiritual purposes.
Here are some reasons why a person might want to fast…
1.) To strengthen prayer
2.) To seek God’s guidance
3.) To express grief
4.) To seek deliverance or protection
5.) To express repentance and the return to God
6.) To humble oneself before God
7.) To express concern for the work of God
8.) To minister to the needs of others
9.) To overcome temptation and dedicate yourself to God
10.)To express love and worship to God
Fasting can be an expression of finding your greatest pleasure and enjoyment in life from God. That’s the case when disciplining yourself to fast means that you love God more than food, that seeking him is more important to you than eating. This honors God and is a means of worshiping him as God. It means that your stomach isn’t your god as it is with some (Philippians 3:19). Instead it is God’s servant, and fasting proves it because you’re willing to sublimate its desires to those of the Spirit.
Fasting must always have a spiritual purpose – a God-centered purpose, not a self-centered one – for the Lord to bless our fast. Thoughts of food must prompt thoughts for God. They must not distract us, but instead remind us of our purpose. Rather than focusing the mind on food, we should use the desire to eat as a reminder to pray and to reconsider our purpose.
Fasting should always have a purpose, and we must learn to elevate God’s purpose over ours.
 This material comes from a chapter in Donald Whitney’s excellent book, Spiritual Disciplines for the Christian Life.