Fasting: How Long and How Often?

Moses fasted for 40 days. Twice. Let me say up front that I’m not recommending that.

In the book of Exodus we read that Moses spent 40 days with the Lord on Mount Sinai, where he received stone tablets with the law inscribed by the finger of God (Exodus 24:18, Exodus 31:18). After destroying those tablets, he ascended the mountain again, where the Lord inscribed a new set of tablets (Exodus 34:28). Moses later explained to the Israelites that he had abstained from food and water during both of those visits. (See Deuteronomy 9:9, 18.)

How was that possible, especially since human beings can’t survive more than a few days without water? Probably because Moses was transfigured to be with God—his body was temporarily changed into a more holy state that could endure God’s presence. (See Moses 1:11, 14.)

Two other miraculous 40-day fasts appear in the Bible. Elijah was able to abstain from food and drink while traveling to Mount Horeb (another name for Mount Sinai), after eating a meal provided by an angel. (See 1 Kings 19:8.) And the Savior began His ministry with a forty-day fast in the wilderness. (See Matthew 4:2, Luke 4:1-2.)

What was the purpose of these fasts? Moses specifically described his second fast as an intensification of his prayer, a way of showing God that his petition was sincere and serious. (See Deuteronomy 9:18-20.)

The Book of Mormon also describes people fasting in conjunction with prayer. Alma fasted and prayed as his son lay in a coma for two days. (See Mosiah 27:22-23.) His son (also named Alma) “fasted and prayed many days” to know whether his father’s teachings were true (Alma 5:45-46). I think this means that he fasted multiple times, not one time for multiple days. Years later, this younger Alma was astounded at the spiritual maturity of his friends, the sons of Mosiah, which was partly a result of consistent fasting over time. “They had given themselves to much prayer and fasting,” the record says (Alma 17:3).

Mormon writes about a group of church members whose hearts were purified and sanctified because they “did fast and pray oft” (Helaman 3:35). And Amaleki admonished us—his future readers—to “offer [our] whole souls as an offering unto [God], and continue in fasting and praying” (Omni 1:26).

Members of The Church of Jesus Christ of Latter-day Saints generally skip two consecutive meals on the first Sunday of each month. They may also choose to fast at other times for specific purposes. (See “Fasting” on

A couple of years ago, near the beginning of the COVID-19 pandemic, President Russell M. Nelson invited us to participate in two worldwide fasts, on March 29, 2020, and then again on Good Friday, April 10, less than two weeks later. He explained:

The doctrine of fasting is ancient. It has been practiced by biblical heroes from the earliest days. Moses, David, Ezra, Nehemiah, Esther, Isaiah, Daniel, Joel, and many others fasted and preached of fasting…..

So tonight, my dear brothers and sisters, in the spirit of the sons of Mosiah, who gave themselves to much fasting and prayer…I am calling for another worldwide fast. For all whose health may permit, let us fast, pray, and unite our faith once again. Let us prayerfully plead for relief from this global pandemic.

Opening the Heavens for Help,” General Conference, April 2020

And he gave the following guidance about the duration of the fast:

How do we fast? Two meals or a period of 24 hours is customary. But you decide what would constitute a sacrifice for you, as you remember the supreme sacrifice the Savior made for you.

Opening the Heavens for Help,” General Conference, April 2020

I love the implications of this counsel. Fasting once a month may be a default pattern, but we may fast at other times as we strive to draw closer to God. 24 hours may be customary, but a shorter fast may be appropriate for some people. I love President Nelson’s encouragement to catch the spirit of the fast: “You decide what would constitute a sacrifice for you.”

This Sunday, as I fast, I will remember the many people throughout history who have experienced spiritual growth by fasting and praying regularly. I will remember that a pattern of fasting over time can have a sanctifying effect on my heart, and that I can fast in a way that is appropriate to my circumstances.

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