2 Chronicles 20: 1-4
1 After this, the Moabites and Ammonites with some of the Meunites came to make war on Jehoshaphat.
2 Some men came and told Jehoshaphat, “A vast army is coming against you from Edom, from the other side of the Sea. It is already in Hazazon Tamar” (that is, En Gedi). 3 Alarmed, Jehoshaphat resolved to inquire of the LORD, and he proclaimed a fast for all Judah. 4 The people of Judah came together to seek help from the LORD; indeed, they came from every town in Judah to seek him.
Could it be that fasting helps the individual to focus on God wholeheartedly?