Introduction
According to the Bible, fasting means giving up food for a time in order to turn toward God in prayer, mourning, repentance or an important decision. It is neither a way to lose weight nor a way to earn God's favor. Jesus presents it as a discreet act, lived before the Father alone.
Fasting intrigues and sometimes worries people. Some see it as a spiritual feat, others as a practice from another era. Yet the Bible speaks of it from beginning to end, simply. This page surveys the Old Testament, the teaching of Jesus and the text of Isaiah 58, then offers wise guidelines, including on health.
Fasting in the Old Testament
In the Old Testament, people fasted in serious moments: mourning, danger, a fault to acknowledge. Queen Esther asks all her people to fast before she appears before the king, at the risk of her life. Daniel partially fasts for three weeks in mourning and prayer.
The prophet Joel calls people to return to God with all their heart. Fasting is therefore not a technique, but an outward sign of an inward attitude: humility, need for God, desire to turn toward him. Without the heart, the gesture says nothing.
Esther 4:16
"Go, gather together all the Jews who are present in Susa, and fast for me, and neither eat nor drink three days, night or day. I and my maidens will also fast the same way. Then I will go in to the king, which is against the law; and if I perish, I perish."
Esther calls for a communal fast before a risky step. The fast expresses dependence: she does not rely on her own skill alone, but seeks God's help with her people. Read all of Esther 4.
Joel 2:12
"Yet even now,” says Yahweh, “turn to me with all your heart, and with fasting, and with weeping, and with mourning."
God calls his people to return to him with all their heart. Fasting accompanies this return, along with weeping. What matters is the sincerity of the step. Read all of Joel 2.
What Jesus Teaches About Fasting
Jesus himself fasts forty days in the desert before beginning his ministry. He gives no precise rule, but he says "when you fast," which assumes his disciples will practice it. Above all, he corrects the intention: fasting is not meant to be seen or admired.
He invites us to fast in discretion, before the Father who sees in secret. This protects against two traps, spiritual pride and comparison with others. Christian fasting is a conversation with God, not a display.
Matthew 4:1-2
"Then Jesus was led up by the Spirit into the wilderness to be tempted by the devil. When he had fasted forty days and forty nights, he was hungry afterward."
Jesus fasts before being tempted in the desert. This account shows that fasting can accompany a time of preparation and dependence, without being presented as a rule for everyone. Read all of Matthew 4.
Matthew 6:16-18
"Moreover when you fast, don’t be like the hypocrites, with sad faces. For they disfigure their faces, that they may be seen by men to be fasting. Most certainly I tell you, they have received their reward. But you, when you fast, anoint your head, and wash your face; so that you are not seen by men to be fasting, but by your Father who is in secret, and your Father, who sees in secret, will reward you."
Jesus asks us to fast without seeking the gaze of others. He teaches us that God sees what is hidden, and that the reward is not measured by what people notice. Read all of Matthew 6.
What Is True Fasting According to Isaiah 58?
In Isaiah's time, people fasted zealously while treating their workers unjustly. The prophet conveys God's answer: the fast he desires shows itself in daily life. It frees the oppressed, shares bread and opens one's home to those who have none.
This text does not eliminate fasting from food; it reveals its meaning. Going without has value only if it makes us more attentive to God and to others. A fast that leaves us indifferent to the suffering around us has missed its purpose.
Isaiah 58:6-7
"Isn’t this the fast that I have chosen: to release the bonds of wickedness, to undo the straps of the yoke, to let the oppressed go free, and that you break every yoke? Isn’t it to distribute your bread to the hungry, and that you bring the poor who are cast out to your house? When you see the naked, that you cover him; and that you not hide yourself from your own flesh?"
Here God defines the fast that pleases him: justice and generosity. A sincere sacrifice opens our eyes to the needs of others and shows up in concrete acts. Read all of Isaiah 58.
Why Fast?
The Bible gives several reasons. People fast to pray with greater attention, to seek God's direction before a decision, to mourn, or to acknowledge a sin and return to him. In the book of Acts, a community fasts and prays before sending two of its members on mission.
In all these cases, fasting supports prayer and does not replace it. It can help us detach from noise and appetite in order to listen to God. But it does not oblige God to answer, and it does not make anyone more loved by him.
Acts 13:2-3
"As they served the Lord and fasted, the Holy Spirit said, “Separate Barnabas and Saul for me, for the work to which I have called them.” Then, when they had fasted and prayed and laid their hands on them, they sent them away."
A community fasts and prays before sending out its missionaries. Fasting accompanies a shared time of listening and decision, in prayer and service. Read all of Acts 13.
How to Fast Wisely
Start modestly. You can skip a meal, or fast for a day while drinking water, taking time to pray and read. Fasting can also take other forms, such as giving up screens or some pleasure. Longer fasts require experience and medical advice.
If you have doubts about your health, talk to a doctor first. Fasting should never become a diet to lose weight, nor a way to punish yourself or earn God's love, which is already given by grace. Good practice keeps joy, gentleness and respect for the body God created.
Who Should Not Fast From Food?
Some people should refrain from fasting from food: pregnant or breastfeeding women, children, people with diabetes or on treatment, those who suffer or have suffered from eating disorders, and older or frail people. For them, medical caution comes first.
This does not deprive them of the spiritual dimension. You can give up something else, such as social media, television or a comfort habit, and devote that time to prayer. God looks at the heart, not at the quantity of food one gives up.
Further reading
Frequently Asked Questions
How long should you fast according to the Bible?
The Bible sets no fixed length. It records fasts of one day, three days, three weeks, and forty days for Jesus. The wisest approach is to start with a meal or a day, with a doctor's advice if you have doubts about your health.
Can you drink water while fasting?
Yes, and it is even recommended for health. The Bible mentions fasts without food or drink, but these are rare, short and tied to exceptional situations. For an ordinary fast, drinking water is prudent. A doctor can advise you if you are on treatment.
Is fasting a way to lose weight?
No. Biblical fasting is a spiritual act, directed toward God, not a diet. Seeking an aesthetic goal distorts its meaning. If you want to lose weight, a health professional can support you, and you can keep fasting for prayer.
Does God answer better when you fast?
The Bible does not present fasting as a way to obligate God. It expresses humility and the desire to seek him. God listens to those who pray without fasting. Fasting can help us listen, but it is never a condition for being answered.