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Biblical Fasting: Why, When, How, and How Not to Fast

The concept of fasting is pervasive in the Bible. The practice of fasting, for multiple reasons, was well known to people in the ancient world—from prophets and priests to princes and paupers. A discipline intentionally engaged in by millions of people throughout the centuries, it is still practiced today.

The practice of refraining from eating or drastically reducing our food intake for a certain amount of time can focus our thoughts and sharpen our responses to certain situations. When we break from our regular routines of eating at certain times of the day, we allow our bodies to assist our minds in understanding that, for a time, we are going to be denying ourselves one thing in the interest of pursuing or considering another, typically higher, question or goal.

Why Should We Fast?

Why do people fast? While in the modern world, fasting has become popular for weight loss and other purported health benefits, individuals and people groups in ancient times fasted to show their devotion to their deity, to demonstrate the depth of their sorrow over a sin or some situation in their lives, or to show their commitment to a certain cause—among other reasons.

Author, editor, and professor Joe Carter has collected ten reasons for biblical fasting1:

1. To strengthen prayer (e.g., see Ezra 8:23)
2. To seek God’s guidance (e.g., see Judges 20:26)
3. To express grief (e.g., see 1 Samuel 31:13)
4. To seek deliverance or protection (e.g., see 2 Chronicles 20:3 – 4)
5. To express repentance and a return to God (e.g., see 1 Samuel 7:6)
6. To humble oneself before God (e.g., see 1 Kings 21:27 – 29)
7. To express concern for the work of God (e.g., see Nehemiah 1:3 – 4)
8. To minister to the needs of others (e.g., see Isaiah 58:3 – 7)
9. To overcome temptation and dedicate yourself to God (e.g., see Matthew 4:1 – 11)
10. To express love and worship for God (e.g., see Luke 2:37)

Christians who want to pursue a fast will benefit from studying other instances in the Bible where fasting was practiced. To pursue this kind of topical study, a simple internet search will bring up many different resources.

But the prophet Isaiah provides us with perhaps the clearest explanation and understanding of fasting in the Bible. Portions of Isaiah 58 (emphases mine) will serve as a framework for studying why, how, when, and why Christians today should pursue fasting:

“Shout it aloud, do not hold back.
Raise your voice like a trumpet.
Declare to my people their rebellion
and to the descendants of Jacob their sins.
For day after day they seek me out;
they seem eager to know my ways,
as if they were a nation that does what is right
and has not forsaken the commands of its God.
They ask me for just decisions
and seem eager for God to come near them.
Isaiah 58:1–2

Here we see that fasting is good for multiple reasons: to seek God out; to know his ways; to pursue answers to decisions that are coming into play in one’s life; and to intentionally draw closer to him. All of these reasons are wonderful goals to pursue for individuals whose hearts are right and whose motivations are pure. Jesus said, “Come to me, all you who are weary and burdened, and I will give you rest. Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls. For my yoke is easy and my burden is light” (Matthew 11:28–30).

God desires that his people come to him in all situations to seek out his guidance and direction. He cares for us in all situations, because he knows us better than we know ourselves. David spoke the following truth in Psalm 139: “All the days ordained for me were written in your book before one of them came to be” (v. 16). Since this is the case, there’s no better reason for Christians to turn to God for direction. And during these periods in our lives, fasting can sharpen the urgency and intensity of that search.

How Should We Fast?

The first imperative in deciding to fast is that we do so out of a sincere desire to seek God’s guidance and direction. Fasting for the sake of making a show in front of others, or fasting to ask God for things that are clearly outside of his will, is an exercise in futility. More on that in a minute.

First, let’s look at the physical aspects of fasting. Fasting comes in different forms and is done in different ways. The most important factors to consider in starting a fasting regimen include the following:

Your Personal Reasons for Pursuing a Fast.

If you’re on the cusp of a major life change, are grieving the loss of a certain individual or period in your life, or are seeking answers from God for an upcoming decision, the reasons you choose to fast are unique to you. Consulting with others about their experiences can be instructive, but your choice to fast and the reasons for your fast are unique to your situation.

The Method of Fasting You Want to Pursue.

Fasting doesn’t necessarily involve a complete cessation of eating; it can be done by cutting down the number of calories you ingest for a certain period of time as well. For many people, however, the time and focus saved on preparing and eating food work well to change their focus to the issue at hand. Still, if you try a complete fast and find that you’re distracted by the lack of food, consider simply cutting your caloric intake back drastically and eat small amounts of food during your fast. Experts recommend 500 calories per day for women, and 600 calories per day for men.

The Duration of the Fast.

Fasting can be done on a daily, weekly, or annual basis. Many people who choose to fast do so intermittently, such as during a portion of their workday, to focus on seeking God for an hour or two, and then they go back to a regular eating schedule. Others find benefits in fasting during a certain time of the month or year to pursue guidance and direction from God. Again, the duration and length of your fast are personal decisions only you can make.

The Time You Have to Focus.

Fasting requires intense focus on the reasons for your fast and on listening to God during this period of time. You’ll want to clear your calendar of extraneous activities so you can calm your heart and mind as you seek God’s face. Ideally, setting aside specific time in your calendar to focus on prayer and study during your period of fasting will help. Spending an overnight in a location where you (or your group, if you’re fasting with others) can get away from city lights and noise or the distractions of family obligations can increase the effectiveness of the fast.

Your Physical Space.

Selecting the right physical space is important for fasting. To reduce your temptation to eat and to sharpen your focus during your fast, consider setting aside space in your home or in another familiar space for prayer and meditation. While you’re fasting, move to that space to pray during the times you would normally be eating. If you can, during your typical mealtimes, move out of your food-related context by taking a walk, going for a drive, or sitting outdoors.

Your Own Personal Health.

While individuals in the Bible fasted for extended periods of time (see Matthew 4), before you fast for any period longer than twenty-four hours, please consult your doctor. Fasting for a longer period of time can lead to dehydration and have other detrimental health effects, especially if you suffer from conditions such as diabetes that may require you to eat at certain times and monitor your body’s sugar levels. If during the course of your fast you start to feel ill, stop fasting and ease back into eating.

Breaking your fast.

Experts recommend coming out of a period of fasting, not by feasting, but by starting slowly and being disciplined to eat only regular portions. While you may be hungry and inclined to overindulge after a fast, your goal should be to return to a normal eating pattern.

Remember, nowhere in Scripture are individuals encouraged to fast to the detriment of their health. When individuals and people groups called for fasting, it was typically for a specific period of time with a well-defined starting and ending point.

Now let’s get back to the condition of your heart before you begin the fast. Again, let’s look at Isaiah 58 as we consider this important factor:

‘Why have we fasted,’ they say,
‘and you have not seen it?
Why have we humbled ourselves,
and you have not noticed?’
Isaiah 58:3

This implies that the people who engaged in the fast did so for a certain period of time for a certain personal reason. At this point in the conversation, perhaps they had completed their fast and were frustrated with the results: they had gone into their fast period with a certain goal in mind, and their goals were not accomplished. Even though they had correctly pursued the “how” of the fast, their fast didn’t have its intended effect.

Before you start your fast, review the list above several times and dig deeply to understand your motivations. Be clear on what you’re fasting for, and why, before you decide on how.

How Not to Fast

The prophet Isaiah instructs his readers about pursuing a fast while one’s heart is not in the right place (again, emphases mine):

“Yet on the day of your fasting, you do as you please
and exploit all your workers.
Your fasting ends in quarreling and strife,
and in striking each other with wicked fists.
You cannot fast as you do today
and expect your voice to be heard on high.

Is this the kind of fast I have chosen,
only a day for people to humble themselves?
Is it only for bowing one’s head like a reed
and for lying in sackcloth and ashes?
Is that what you call a fast,
a day acceptable to the LORD?

Isaiah 58:4–5

This passage speaks to the heart and practice of people who fast to put on a show or whose motivations are not pure. Fasting is done with open hearts and hands to receive guidance and direction from God, not as a tool to manipulate God into conforming his divine will to one person’s plans.

Isaiah calls out the individuals in question, relating God’s desire for authenticity from those who seek him.

Fasting as a Worldview

Finally, let’s explore the prophet Isaiah’s words regarding the practice of fasting, of pursuing answers from God or showing one’s remorse over a certain life situation. In this, Isaiah clarifies what God wants to see in our lives when we fast—namely, a sincere devotion to himself and others without self-imposed blinders for the situations around us.

Individuals who fast to seek answers to their questions can’t ignore the other dictates of the Bible or the situations around them where they are called to become the hands and feet of God in their circle of influence. In short, fasting is futile if we’re asking questions for which the answers lie outside the will of God.

In the following passages, Isaiah calls out the people for their refusal to act in ways that would truly reflect their personal devotion to God and his purposes in the world (emphases mine):

Is not this the kind of fasting I have chosen:
to loose the chains of injustice
and untie the cords of the yoke,
to set the oppressed free
and break every yoke?

Is it not to share your food with the hungry
and to provide the poor wanderer with shelter—

when you see the naked, to clothe them,
and not to turn away from your own flesh and blood?
Isaiah 58:6–7

But the chastising we read in Isaiah 58 does not come without hope and a promise—a promise that was as true for its initial hearers as it is for us today.

When we pursue the purposes of God in our hearts and our lives, we connect more closely to the heart of God. When we change our practices—literally, when we change what we do and why—and when we go beyond merely external fasting and understand more clearly how God wants us to live, we can expect to experience more of the following:

Then your light will break forth like the dawn,
and your healing will quickly appear;
then your righteousness will go before you,
and the glory of the LORD will be your rear guard.
Then you will call, and the LORD will answer;
you will cry for help, and he will say: Here am I.

“If you do away with the yoke of oppression,
with the pointing finger and malicious talk,
and if you spend yourselves in behalf of the hungry
and satisfy the needs of the oppressed,
then your light will rise in the darkness,
and your night will become like the noonday.
The LORD will guide you always;
he will satisfy your needs in a sun-scorched land
and will strengthen your frame.
You will be like a well-watered garden,
like a spring whose waters never fail.

Your people will rebuild the ancient ruins
and will raise up the age-old foundations;
you will be called Repairer of Broken Walls,
Restorer of Streets with Dwellings.
Isaiah 58:8–12

Written by Mike Vander Klipp, Senior Editor in the Zondervan Bible Group of HarperCollins Christian Publishing.

For more, read “10 Biblical Purposes for Fasting.”

¹ The NIV Lifehacks Bible, notes by Joe Carter (Grand Rapids, MI: Zondervan, 2016), 317.
² Portions of this section were gleaned from “How to Fast Safely: 10 Helpful Tips,” Healthline, www.healthline.com/nutrition/how-to-fast and Faith Lawyer, “What Time, How Long and When Christians Should Fast,” Just Disciple, October 16, 2019, www.justdisciple.com/christian-fasting-time.


  1. Joe McComb says:

    Very useful.

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  2. Daniel Sonia says:

    This is really beautiful. I’m fasting today and I hope I find what I seek for.

    • Terms and Condition - I agree to the HarperCollins Publishers Terms of Use for Bulletin Boards, Chat Rooms & Blogs.

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