There is spiritual delight to be found in God that far supersedes the physical diet of this world, and fasting is the means by which we say to God, “More than our stomachs want food, our souls want you.” Once we “taste and see that the LORD is good” (Psalm 34:8), the things of the world no longer appeal to us in the same way.
A Hunger for God - Desiring God through Fasting and Prayer" by John Piper.