Notwithstanding that fasting is good for your health, what are the reasons Mormons fast? How often? Is it necessary? We shall see.
Why a Fast?
It is recorded in Scripture that Moses fasted; that for "forty days . . . he did neither eat bread, nor drink water. (Ex. 34:28)" In this instance, Moses was in the Mountain of the Lord in Sinai, and he needed not only revelation, but he also needed to purify himself before God. Fasting is a way to do that. During the April 2001 General Conference, Elder Joseph B. Wirthlin of the Quorum of the Twelve said, "Fasting, coupled with mighty prayer, is powerful. It can fill our minds with the revelations of the Spirit." Who can doubt that during Moses' seclusion atop the Mountain of the Lord he received revelations from the Lord? Any student of the Bible can see from this event that fasting brings revelation. This is also shown during the mortal ministry of Jesus, "when He had fasted forty days and forty nights (Matt 4:2)". That Jesus drew upon the power of fasting and prayer is evident when Christ refuted his fallen brother Satan's temptations by quoting from Scripture, the knowledge of which no doubt came to the Master through study and fasting and prayer.
When I am feeling tempted more than I can bear, or need answers I know I cannot find on my own, I fast one meal. More often than not, the answers do not come immediately, but they do come. I know fasting is a principle laid down by the Lord that His children might draw closer to Him.
How Often Must We Fast?
Elder Wirthlin taught, "In The Church of Jesus Christ of Latter-day Saints, members are encouraged to fast whenever their faith needs special fortification and to fast regularly once each month on fast day. On that day, we go without eating or drinking for two consecutive meals, [and] commune with our Heavenly Father." President Howard W. Hunter taught that "there are records that indicate that some fast meetings were held in the Kirtland Temple on the first Thursday of each month in the year 1836. (Ensign, November 1985)" President Brigham Young elaborates,
You know that the first Thursday in each month we hold as a fast day. How many here know the origin of this day? Before tithing was paid, the poor were supported by donations. They came to Joseph and wanted help, in Kirtland, and he said there should be a fast day, which was decided upon. It was to be held once a month, as it is now, and all that would have been eaten that day, of flour, or meat, or butter, or fruit, or anything else, was to be carried to the fast meeting and put into the hands of a person selected for the purpose of taking care of it and distributing it among the poor (JD 12:115)
The first Thursday of every month was Fast Day until, as President Hunter states, "the first Sunday of December, 1896, was the date set for the change. From that time to the present—nearly a century—the fast day has been observed, in most instances, on the first Sunday of the month as a religious practice."
I know that fasting is a commandment of the Lord Jesus Christ. I know that if anyone on Earth has a question, burden, or spiritual or temporal need, fasting will alleviate that need. I know that The Church of Jesus Christ of Latter-day Saints is the only true and living church on the earth; that God established it for the eternal salvation of man, both living and dead. In the Name of Jesus Christ, amen.