The scriptures: What follows are the Scriptures on the subject of fasting. My impression is that fasting happens when the people of God seek to humble themselves and acknowledge that the situation they are in requires the intervention of God. They seek the favour of God and will not allow their physical needs to interfere. Then fasting is not planned but it takes place as a result of their seeking God.

God is able to engineer circumstances so that we deal directly with Him. A personal example: We were required to raise our personalised support in 1980. The church we were in were not interested as they believed they gave as the Lord led. Trouble is they all received salaries every month, but never considered their missionaries needed their expenses to be covered monthly. Promises were made but not kept. Words are cheap.
One SA missionary couple had to return home as a result of no involvement by the local church. In our case I sought the Lord. I received a reply to my request which was, ”What would you have me to do ? “Nothing. Just trust Me. I will fill your mouth with laughter.”
I no longer raised the subject. I thoroughly enjoyed my deputation. God gave us over 100% monthly support. I led my sister to faith in Jesus. Indeed He filled my heart with laughter.

So I believe, and most likely I am ignorant, that fasting is a state of mind and body that is the result of a servant of God not allowing personal physical needs to interfere in their seeking the intervention and favour of the Lord.

As I type, I remember Dawie Pypers (the DRC missionary who worked amongst Moslem and Hindus) responded to a challenge by Ahmat Deedat in 1961 to engage him in debate on the subject of the life, death, burial and resurrection of Jesus.
The archbishop of Cape Town turned down the challenge, but Dawie felt it was a disgrace and took his place.
Dawie spent about two weeks fasting and in prayer about how to respond in the debate. What to say and what to do. He was Afrikaans speaking yet called to debate in English.
Eventually he was given the liberty to say that Jesus is alive and would heal anyone of any disease as evidence that He is alive.
I was there! A fellow student from the Bible Institute was horrified. Yet a lady was healed and later joined Dawie in his ministry.
God continued to use Dawie in His ministry in healings.
Once he was preaching on the "I Am"s of Jesus in a coloured township. A Moslem lady lying ill in bed where she had been confined for many months cried out to Allah, but nothing happened then spoke to Muhammad, but nothing happened. Then she cried out to Jesus and was healed. She then told Dawie how Jesus had healed her.
You can imagine the response! Moslem leaders tried to silence her. She told them how Jesus had healed her and they picked up their books and left.
Dawie reaped the blessing of dealing directly with God. His ministry was radically changed. How do I know this? He and his wife stayed with us when we studied Arabic in Jordan.

Fasting indicates a commitment to seek God with all the heart and allow nothing to intrude. Perfectly normal acts of eating or drinking to meet the needs of the body are relegated in a desire to get God to intervene in such as way that He gets all the glory.
Fasting if it is part of life like going to worship or setting aside time to do so – could be just another habit of man. Fasting as the result of single-minded seeking after God and requesting His involvement in reaching the lost and equipping His saints with Holy Spirit power that Jesus might be restored in the proclamation of the good news of salvation, is I believe the only form of fasting that will result in the extension of the Kingdom of God.
Fasting as a habit could give the idea of pride as a result of regarding it as good works.
Jesus told us that no one should know we are fasting. It is between us and the Lord. Same applies to prayer and Bible study. It is personal and private. God who alone sees the fasting or prayer will reward His children openly. In other words spiritual private dealings with God will result in a change in appearance of the individual.

It reminds me of Keith who came to faith in Christ at the golf driving range. A year later I saw him. His face was shining. Jesus was in His rightful place in his life.
Isaiah 58:6-7 '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 him and not to turn away from your own flesh and blood?'
God is saying that a relationship with Himself results in a change of behaviour. It is practical. It affects all of life. No longer life divided into pockets. Fasting. Not fasting. Praying. Not praying. Bible reading. Not Bible reading.
God wants us to be His people moving amongst His creation with a radical change of behaviour. Our relationship with Him uppermost in our minds. Him outworking His salvation in a world leaving Him out of their lives.

The Scriptures:

Matthew 9:15 'How can the guests of the groom mourn while he is with them? The time will come when the groom will be taken from them, then they will fast.'
Leviticus 23:27-29 Fasting required on the day of atonement
Colossians 2:13-23 'When you were dead in your sins and the uncircumcision of your sinful nature, God made you alive with Christ. He forgave us all our sins, having canceled the written code with its regulations that was against us and stood opposed to us, He took it away nailing it to the cross. And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross. Therefore do not let anyone judge you by what you eat or drink or regard to a religious festival a New Moon celebration or a Sabbath Day. These are a shadow of the things that were to come. The reality is found in Christ... Do not let anyone disqualify you for the prize... He has lost connection with the Head from whom the whole body grows as God causes it to grow... You died with Christ. Do not let the world that you once belonged to cause you to lose your freedom in Christ through regulations, self imposed worship, false humility and harsh treatment of the body.' Your life is now hidden with Christ in God. Put to death the sinful nature. Get rid of anything that belongs to the old sinful nature. No longer a life of rules but a relationship with Jesus through the enabling of the Holy Spirit.
2 Chronicles 20:2-3,12 'A vast army came from Edom... Jehoshaphat resolved to inquire of the Lord and proclaimed a fast for all Judah who came together to seek help from the Lord... 12 We have no power to face this vast army. We do not know what to do but our eyes are upon You.'
Jonah 3:5-9 'The Ninevites believed God. They declared a fast. The king declared: Do not let any man or beast taste anything, nor eat or drink. Let everyone call urgently on God. Let them give up their sinful ways and violence. Who knows? God may yet relent and with compassion turn from His fierce anger so that we will not perish.'
1 Samuel 7:5-6 'Samuel said, assemble all Israel at Mizpah and I will intercede with the Lord for you. On that day they fasted and confessed “we have sinned against the Lord.”'
Joel 2:12-13 'Even now declares the Lord, return to me with all your heart with fasting and weeping and mourning. Rend your heart and not your garments. Return to the Lord your God for He is gracious and compassionate. Slow to anger and abounding in love and He relents from sending calamity'
Ezra 8:21-23 'I proclaimed a fast that we might humble ourselves before God... The gracious hand of our God is on everyone who looks to Him... So we fasted and petitioned our God about this, and He answered our prayer.'
Nehemiah 9:1 'The Israelites gathered together, fasting and wearing sackcloth'
Esther 4:16 'Gather all the Israelites and fast for me for 3 days and I will fast. I will go even though it is against the law and if I perish, I perish.'
Acts 13:2-3 'While they were worshipping the Lord and fasting, the Holy Spirit said, "Set apart for Me Barnabas and Saul for the work to which I have called them." So after they had fasted and prayed, they placed their hands on them and sent them off.'
Acts 14:23 'Paul and Barnabas appointed elders in each church... with prayer and fasting'

Persons:Exodus 34:28 Moses was with the Lord for 40 days and 40 nights without eating bread or drinking water.

Deuteronomy 9:18 40 days - ate no bread nor drank water
Matthew 4:1-4 'Jesus was led by the Spirit into the desert to be tempted by the devil. After fasting 40 days and 40 nights He was hungry. The tempter came to Him and said, If You are the Son of God tell these stones to become bread. Jesus answered,”It is written man shall not live by bread alone but on every word that comes from the mouth of God'
Daniel 9:3 'I turned to the Lord God and pleaded with Him in prayer and fasting.'

Purpose of Fasting:

To get God’s attention
Isaiah 58:1-11 Why did their fasting not get God’s attention? Because they still did as they pleased. They enjoyed the activity as part of life it made them feel good and self righteous.
Psalm 139:1-3 'Lord You have searched me and You know me. You know when I sit and when I rise You perceive my thoughts from afar. You discern my going out and my lying down. You are familiar with all my ways.'
In other words we do not need to fast to get God’s attention.
Does God change His mind?
2 Kings 20:1-6 'Hezekiah was sick and on the point of death. Isaiah said, ”Put your house in order because you are going to die. You will not recover.” Hezekiah prayed, “Remember O Lord how I have walked before You faithfully and with wholehearted devotion and done what is good in your sight. He wept bitterly. God came to Isaiah, Tell Hezekiah “I have heard your prayer and seen your tears. I will heal you. You will go to the temple on the third day. I will add 15 years to your life, and deliver this city from the king of Assyria.”'
2 Samuel 7:1-17 David wanted to build a temple. He was told his son would build that temple His house would endure forever.
Jonah 3:9 'Who knows?'

We cannot limit God. He will never act contrary to His Word.
What we do not know, is how He involves man in the decisions that He takes. To allow His servants to be involved in His activity. As though their requests caused Him to change His mind. Whereas He planned it that way long before the interaction.
1 Kings 21:27-29 Ahab was told that disaster awaited his family because of the death of Naboth. He humbled himself and was told that all the disasters that would overtake his family would only happen after his death.
Isaiah 55:6-9 'Seek the Lord while He may be found; call on Him while He is near. Let the wicked forsake his way and the evil man his thoughts. Let him turn to the Lord, and He will have mercy on him, and to our God, for He will freely pardon. "For My thoughts are not your thoughts, neither are your ways My ways" declares the Lord. "As the heavens are higher than the earth so are My ways higher than your ways and My thoughts than your thoughts."'
Ephesians 5:17 'Be not foolish but understand what the Lord’s will is.'

Continued blessing?
Acts 13:2 While they were worshipping the Lord and fasting the Holy Spirit said,” Set apart for the works to which I have called them.”
Acts 14:23 Appointed elders in each church with prayer and fasting

Matthew 17:19-20 '"Why could we not drive it out?"... "Because you have so little faith. If you have faith as a mustard seed... nothing will be impossible for you."'
Mark 9:29 'This can only take place by prayer'
Psalm 35:13-14 'When they were ill, I put on sackcloth and humbled myself with fasting. My prayers returned to me unanswered'
Psalm 109:24 'My knees give way from fasting, my body is thin and gaunt.'
Drink plenty of liquid, do not fast if you have a health problem.
2 Corinthians 2:11 Evil one could attack

Danger of self righteousness
Luke 18:11-13 The Pharisee stood and prayed about himself. "God I thank you that I am not like other men." Robbers ,evil doers, adulterers, or even like this tax collector. "I fast twice a week and tithe all I get." The Tax Collector prayed, beat his breast.
Let that which is taking place on the altar include me.
Matthew 6:16-18 'When you fast do not disfigure your face. Put oil on your head and wash your face, so that it will not be obvious to men that you are fasting, but only to your Father who sees what is done in secret will reward you"
John 5:44 'How can you believe if you accept praise from one another, yet make no effort to obtain praise the comes from the only God.'

Fasting seems to be mainly Old Testament action.

I have never been able to fast except when I am busy with a project and I do not eat or think of food to not be distracted.
Fasting then happens, but is a by product of weightier matters.

On a lighter note. I have been working on this chapter for over 3 and a half hours sorting out the material and typing out the verses. I have been fasting! Nothing to eat or drink. It is 9.30 a.m.
I have enjoyed the exercise and sorting out the verses.

Being thin like Ghandi, I could not follow in his footsteps, as he fasted to stop conflict in India and Pakistan.

He did so for an earthly kingdom. He heard about Jesus, but no one showed him the way to Jesus.

I think he respected the person and teachings of Jesus, but never the life changing impact of His life.