I have some notes from a study that I did on fasting and prayer from Isaiah 58, this is the best place to start when considering fasting.
I have been fasting one day a week for many years; unfortunately it started with a wrong motive, I was kind of bargaining with God. After this study in Isaiah the Lord showed me the proper motives for fasting and I have continued in it with great blessing.
A STUDY ON FASTING AND PRAYER - Reading Isaiah 58
1)Improper reasons for fasting
ӢFasting just to get God's attention (v. 3a)
ӢFasting without focusing on the Lord, fasting had become a mere physical exercise with no affliction of soul or seeking after God.(v.3b)
ӢFasting without accompanying humility of heart. Fasting is not a way of impressing God, it is a way to humble ourselves before Him.(v.4)
ӢFasting for a brief external show of religion. Israel fasted merely for outward show.(v. 5)
2) Proper reasons for fasting
ӢTo bring liberation from the bonds of wickedness and to set the oppressed free. Fasting prepares our hearts to hear what God has to say about issues in our life where we need victory.(v.6)
ӢTo relieve us of heavy burdens, replacing our burdens of every-day life with His burdens.(v.6)(see Matthew 11:28-30)
ӢTo increase our sensitivity towards the needs of others, remember not to stay focused on self, but love one another as Jesus loves you.(v. 7)
ӢTo invest ourselves into our physical and spiritual families, becoming more responsive to the needs of brothers and sisters, husbands and wives.(v.7)
3)God's promises to those who fast
ӢInsight and understanding(v.8). God will give wisdom to solve problems and behave with discretion. (see Jeremiah 33:3)
ӢPositive changes in physical well-being (v.8)
ӢA deep sense of what is right (v.8 "your righteousness will go before you")
ӢA sense of immediate access to God in your prayer life(v.9). We do not pray to get God's attention we pray because we have His attention. Sometimes the world and sin can disrupt our fellowship with God, Setting aside time to pray and fast can bring us face to face with whatever has crept into our lives.(see Psalm 66:18 and 1John 1:9)
ӢRelease from spiritual oppression (v.10) and a return to being strengthened by the joy of the Lord.
ӢMoment by moment guidance from the Lord (v.11). Prayer and fasting will heighten our awareness of God's presence and guidance.
ӢPeace through difficult times (v.11)
In Christ,