For the kingdom of God is not eating and drinking, but righteousness, peace and joy in the Holy Spirit. Romans 14:17

Fasting is to abstain from eating. Fasting was an established practice in the time of Christ (Matthew 9:14-15, Mark 2:18-20, Luke 5:33-35) and was also practiced in the early church. Fasting is a voluntary, never a forced activity. During fasting, the blood in your body used for digestive processes or exercise is available to the brain for increased metal exercise. For this reason fasting is an opportunity to increase your spiritual alertness as you study and pray while abstaining from meals.

Jesus assumes his followers will fast, and even promises it will happen. He doesn’t say “if,” but “when you fast” (Matthew 6:16). And He doesn’t say his followers might fast, but “they will” (Matthew 9:15). The Bible gives additional reasons for fasting:

To overcome temptation. Jesus was led to fast for 40 days (Matthew 4:2).

To seek God’s will in a specific matter. The Israelites fasted to determine direction in battle (Judges 20:26), Paul and Barnabas prayed and fasted before choosing elders (Acts 14:23).

To repent from sin. The Israelites fasted as the repented and put away false Gods (1 Samuel 7:6). David fasted and repented of sin (2 Samuel 12:16 and 21:23). Daniel fasted and repented for himself and the people for not having walked in the laws of the Lord (Daniel 9:3). The people of Ninevah repented and fasted (John 3:5).

To increase concern for the work of God. Nehemiah fasted over the condition of Jerusalem (Nehemiah 1:4).

HOW TO FAST

Start small and build from there. Fasting is simple, but it is not easy. Begin fasting from one meal, and then two, working up to a daylong fast. Consider a juice fast at first, abstaining from all food and beverages except for juice, which provides some nutrients and sugar to the body to keep you operating. Never abstain from water during a fast of any kind. 

Consider your surroundings. Keeping away from food can make you irritable, or seem more isolated as you focus on God. Remember your family and friends. Let those who must know about the fast ahead of time. Consider your work and travel schedule, family obligations. You will have less energy. You may have regular commitments to keep. Plan ahead.

Think about what else. Plan out what you will do instead of eating. Prayer and meditation are a great start. Perhaps there are specific activities that go with your reason for fasting—like studying a particular topic or area where you have a decision to make, or an opportunity ahead. Without a purpose to your fasting, it’s just going hungry.

Fasting doesn’t have to be just food. Fasting is abstaining from anything, really, that keeps your mind away from a spiritual purpose. Your health may not enable you to fast from food. But you could fast from TV, or social media, or sports, or some other regular activity that would allow you to focus your heart and mind on Jesus.