In general, the word fast in the biblical understanding, as in the translation from Hebrew "tzum", literally "to tighten the insides" means abstaining from food.
The Latin word for "fast" is "ieiunium," literally meaning "empty intestine." Therefore, fasting is not a division of food into fasting and lean foods, but simply abstaining from food to combat gluttony, so that the spirit can rule over the flesh.
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Now I will give you the words of the Bible and the Holy Fathers and notable priests about fasting:
1. This kind (demons) comes out only by prayer and fasting (Matt. 17:21).
2. Also, when you fast, do not be like the hypocrites, with a sad countenance. For they disfigure their faces that they may appear to men to be fasting. Truly I say to you, they have their reward (Matt. 6:16).
3. Not what goes into the mouth defiles a man, but what comes out of the mouth, this defiles a man (Matt. 15:11).
4. He who regards the day, regards it to the Lord; and he who does not regard the day, does not regard it to the Lord. He who eats, eats to the Lord, for he gives thanks to God; and he who does not eat, to the Lord he does not eat and gives thanks to God (Rom. 14:6).
5. Food does not bring us closer to God: for if we eat, we gain nothing; and if we do not eat, we lose nothing (1 Cor. 8:8).
6. So whether you eat or drink, or whatever you do, do all to the glory of God (1 Cor. 10:31).
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St. Ignatius (Brianchaninov):
The head of virtues is prayer; their foundation is fasting.
The law of fasting, while outwardly a law for the stomach, is essentially a law for the mind. The mind, that king within man, if it wishes to assume and maintain its sovereignty, must first submit to the law of fasting. Only then will it be continually alert and clear; only then can it rule over the desires of the heart and body; only with constant sobriety can it study the Gospel commandments and follow them. The foundation of virtue is fasting. One who fails to observe moderation and due discrimination in food cannot preserve either virginity or chastity, cannot curb anger, but gives in to laziness, despondency, and sadness, becomes a slave to vanity, a dwelling place for pride, which is introduced into man by his carnal state, which arises primarily from luxurious and satisfying meals. "Take heed to yourselves, lest at any time your hearts be overcharged with surfeiting and drunkenness" (Luke 21:34), the Lord commanded. Gluttony and drunkenness impart fatness not only to the body but also to the mind and heart, that is, they lead a person, both in soul and body, into a carnal state. A carnal person is completely immersed in sinful pleasures. He is sensual in body, heart, and mind, incapable not only of spiritual pleasure and the reception of Divine grace, but also of repentance. He is incapable of spiritual pursuits altogether: he is nailed to the earth, drowned in materiality, alive—dead in soul. Fasting brings a Christian into a spiritual state. Purified by fasting, he is humble in spirit, chaste, modest, silent, refined in the feelings of the heart and thoughts, light in body, capable of spiritual struggles and contemplation, capable of receiving Divine grace.
Archimandrite Raphael (Karelin):
According to Church teaching, physical fasting should be combined with spiritual fasting: abstaining from spectacles, from idle and, especially, immodest conversations, from anything that excites the senses and distracts the mind. Fasting should be accompanied by solitude and silence, reflection on one's life, and self-judgment. According to Christian tradition, fasting begins with mutual forgiveness of offenses. Fasting with malice in the heart is like the fast of a scorpion, which can go without food longer than any other creature on earth, yet produces a deadly venom. Fasting should be accompanied by mercy and assistance to the poor. Fasting should be combined with prayer. Prayer is the soul's turning to God, a mystical conversation between creation and its Creator. Fasting and prayer are two wings that lift the soul to heaven.
Fr Ioann (Kurmoyarov):
Fasting is simply an ascetic exercise for cultivating the will. A sick person's fast should naturally differ from a healthy one's. Abstinence need not only involve abstaining from certain foods, but also reducing their consumption. I advise people with stomach problems to simply limit themselves as much as possible to the foods they particularly enjoy, and only if their doctor allows it. Of course, overeating on Lenten foods is also possible; in other words, fasting is generally abstinence from overeating. But it's important to adhere to the golden rule of the Holy Fathers: the Fathers said that the body is a donkey that carries us to the Kingdom of Heaven. We must not overfeed it, lest it go berserk and throw us off halfway, but underfeeding it would also be a mistake, as it could die halfway. Reason must be observed in all things. Again, fasting is simply a training of the will, the ability to limit oneself in some ways, and food itself neither brings us closer to God nor distances us from Him.
St. John Chrysostom:
“And abstinence from food is adopted in order to weaken the strength of the flesh and make this horse submissive to us. The one who is fasting most of all needs to curb anger, accustom himself to meekness and indulgence, have a contrite heart, cast out unclean desires, imagining that unceasing fire and impartial judgment, be above financial calculations, show great generosity in almsgiving, cast out from the soul all malice towards one’s neighbor. This is the true fast, as Isaiah says on behalf of God: “Is this the fast that I have chosen, a day wherein a man afflicts his soul, when he bows his head like a bulrush, and spreads sackcloth and ashes beneath him? Will you call this a fast and a day acceptable to the Lord?” (Isaiah 58:5). What then, tell me? “Loose,” He says, “the chains of iniquity, ... share your bread with the hungry; ... bring the wandering poor into your home." And when you do this, he says, "then your light will break forth like the dawn, and your healing will quickly grow." You see, beloved, what true fasting consists of. We will observe such a fast, not considering it, like many, merely to remain without food until evening. This is not the main thing, but that with abstinence from food we combine conversations on the book of Genesis and abstinence from what is harmful (to the soul), and show great care for the performance of spiritual works. The one fasting must be calm, quiet, meek, humble, disdaining the glory of this life. Just as he disdained his soul, so he must disdain vain glory and look only to Him Who searches the hearts and inward parts, with great zeal to make prayers and confessions before God, and, as much as possible, help himself with alms. This, this very virtue, can especially erase our sins and snatch us from the fires of Gehenna, if we fulfill it generously, and not for show to others. ... And we will observe this not only in regard to almsgiving, but also in every spiritual work; we will do nothing for the sake of human glory, for there is no benefit to us from fasting, nor from prayer, nor from almsgiving, nor from any other deeds, if we do them not for the sake of the One Who knows both the secret and hidden in the depths of our souls. "He is mistaken who believes that fasting consists only in abstaining from food. True fasting is the removal of evil, the curbing of the tongue, the putting aside of anger, the taming of lusts, the cessation of slander, lies, and perjury."
Saint John of Kronstadt:
Is fasting necessary, as abstinence from disordered thoughts and movements of the heart, and from unacceptable actions? ...You know that an unrighteous thought is an abomination to the Lord (Proverbs 15:26), that God asks for your heart, which you have given over to the will of passions, that no evil (Psalm 5:5) or impurity will dwell with Him. If you want to be with God, if you want to be eternally prosperous, then you must agree that you must fast with your soul, collect your mind, correct your thoughts, purify your thoughts, and, instead of the rags of unrighteous deeds, adorn yourself with the precious garment of good deeds. Bodily fasting is instituted so that it is easier for the soul to fast. Or they consider it a sin to eat anything non-meat on a fast day, even due to physical weakness, and without a twinge of conscience they disdain or condemn their neighbors, for example, acquaintances, offend or deceive, cheat with short weights and short measurements, and indulge in carnal impurity. Oh, the hypocrisy, the hypocrisy! Oh, the lack of understanding of the spirit of Christ, the spirit of the Christian faith! Doesn't our Lord God demand of us, above all, inner purity, meekness, and humility? Are not the inner vessels and dishes to be cleansed so that the outer is pure? Isn't external fasting given to aid inner virtue? Why then do we pervert the divine order?
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I think from these words you understand why fasting is necessary: to free ourselves, to purify ourselves, to break away from the earth and earthly pleasures and to strive for God! Everything must be done for His Glory! Christianity is a religion of freedom and love! Sins and passions are slavery, as the Bible says. And fasting is an important component in this struggle to free us from passions and egoism, in short, to remove everything that prevents us from loving Christ and our neighbors and living only for Him! Without this, fasting simply turns into Ramadan, kashrut, a diet, and simply hypocrisy! Fasting should not be periodic, but constant, since our struggle with our sinfulness is constant. You simply must decide for yourself: are certain foods hindering your spiritual life and their quantity? If so, discard them or reduce them as you see fit.
In terms of health risks: I'm hearing this for the first time. On the contrary, fasting (in the proper sense) is actually beneficial and healing. I even heard of a man who was cured of stomach cancer by fasting. And throughout history, many doctors have recommended fasting for the treatment of various ailments. Diseases are caused by gluttony and luxury foods.
Yes, the Church established a system of fasts, but the purpose of this was to train newcomers to at least periodically control their passions and desires. But for those who love God, serve and live for Him every moment, they need no rules. In Love there is no law!
Glory to God for everything!
Amen
P.S.
Lenten Prayer of St. Nicholas of Serbia☦️
Through fasting I rejoice in my hope in You, my Lord, who is coming again.
Fasting speeds up my preparations for Your coming, the only expectation of my days and nights.
Fasting makes my body thinner so that what remains can more easily shine with spirit.
While waiting for You, I do not wish to feed on blood or take life, so that animals may feel the joy of my waiting.
But truly, abstaining from food will not save me. Even if I ate only sand from the lake, You would not have come to me if fasting had not penetrated deeper into my soul.
Through prayer I have come to understand that bodily fasting is rather a symbol of true fasting, very beneficial for those who have just begun to trust in You, and yet very difficult for those who simply practice it.
Therefore, I introduced fasting into my soul to cleanse it from many daring actions and prepare it for You, like a virgin.
And I introduced fasting into my mind in order to drive out of it all dreams of worldly affairs and to destroy all the castles in the air created from these dreams.
I introduced fasting into my heart so that through it my heart would pacify all passions and worldly egoism.
I have introduced fasting into my heart, so that heavenly peace may inexpressibly reign over my heart when Thy raging Spirit meets it.
I prescribe a fast to my tongue, so that it may rid itself of the habit of idle chatter and speak with restraint only those words that clear the way for Your coming.
And I have imposed a fast on my worries, so that they may scatter them all before me, like the wind that disperses fog, so that they may not stand like a thick fog between me and You, and so that they may not turn my gaze back to the world.
And fasting brought my soul peace in the face of the uncreated and created worlds, and humility before people and creatures. And this instilled in me a courage the likes of which I had never known when I was armed with all sorts of worldly weapons.
What did I hope for before starting this post, other than another story told by others and passed on by word of mouth?
The story of salvation through prayer and fasting became my own.
False fasting is accompanied by false hope, just as the absence of fasting is not accompanied by hopelessness.
But as wheel follows wheel, so true fasting follows true hope.
Help me to fast with joy and hope with joy, for You, my most joyful feast, are approaching me with Your radiant smile.
(From "Prayers by the Lake")