What is fasting and how is it used as a spiritual discipline? It's in the Bible, II Chronicles 20:3, TLB. "Jehoshaphat was badly shaken by this news and determined to beg for help from the Lord; so he announced that all the people of Judah should go without food for a time, in penitence and intercession before God."
Fasting is a way of demonstrating our intense need for God's help. It's in the Bible, Ezra 8:21, TLB. "Then I declared a fast while we were at the Ahava River so that we would humble ourselves before our God; and we prayed that He would give us a good journey and protect us, our children, and our goods as we traveled."
Fasting should not be done to impress other people. It's in the Bible, Matthew 6:17-18, TLB. "But when you fast, put on festive clothing, so that no one will suspect you are hungry, except your Father who knows every secret. And He will reward you."
Fasting can involve a simple diet. It's in the Bible, Daniel 10:2,3, NRSV. "At that time I, Daniel, had been mourning for three weeks. I had eaten no rich food, no meat or wine had entered my mouth and I had not anointed myself at all, for the full three weeks."