It is if:  We have decisions to make.  Acts 13:2  While they were worshiping the Lord and fasting, the Holy Spirit said, "Set apart for me Barnabus and Saul for the work to which I have called them." 

It is if:  We desire to hear from God. Acts 10:30  And Cornelius said, "Four days ago I was fasting until this hour; and at the ninth hour I prayed in my house, and, behold, a man stood before me, in bright clothing."Acts 10:31  And said, "Cornelius, your prayer is heard, and your alms are held in Remembrance in the sight of God." 

 As PRAYER adds POWER to FAITH, so FASTING adds POWER to PRAYER.