(This is a bit of a departure from my usual chemistry-focused writing.)
Fasting is an important part of many religious traditions, but modern Protestant Christians don’t really have a unified stance on fasting (and have opposed systematic fasts for a while). That’s not to say that Protestants don’t fast, though: over just the past few years, I’ve met people doing water-only fasts, juice fasts, dinner-only fasts, “social media” fasts, and many more.
These fasts don’t really line up with what I see in neighboring faith traditions:
I’ve been a bit puzzled by all this, so I decided to do a “literature review” and find documents from the early Church that discussed fasting. This post collects and summarizes the sources that I found. The sources are listed in approximate chronological order, with emphasis added throughout—if you don’t want to read everything, you can skip to the end and read my brief takeaways.
But before the baptism let the baptizer fast, and the baptized, and whatever others can; but you shall order the baptized to fast one or two days before….
But let not your fasts be with the hypocrites; for they fast on the second [Monday] and fifth day [Thursday] of the week; but fast on the fourth day [Wednesday] and the Preparation (Friday).
Thus, then, shall you observe the fasting which you intend to keep. First of all, be on your guard against every evil word, and every evil desire, and purify your heart from all the vanities of this world. If you guard against these things, your fasting will be perfect. And you will do also as follows. Having fulfilled what is written, in the day on which you fast you will taste nothing but bread and water; and having reckoned up the price of the dishes of that day which you intended to have eaten, you will give it to a widow, or an orphan, or to some person in want, and thus you will exhibit humility of mind, so that he who has received benefit from your humility may fill his own soul, and pray for you to the Lord. If you observe fasting, as I have commanded you, your sacrifice will be acceptable to God, and this fasting will be written down; and the service thus performed is noble, and sacred, and acceptable to the Lord. These things, therefore, shall you thus observe with your children, and all your house, and in observing them you will be blessed; and as many as hear these words and observe them shall be blessed; and whatsoever they ask of the Lord they shall receive.
Now, if there has been temerity in our retracing to primordial experiences the reasons for God's having laid, and our duty (for the sake of God) to lay, restrictions upon food, let us consult common conscience. Nature herself will plainly tell with what qualities she is ever wont to find us endowed when she sets us, before taking food and drink, with our saliva still in a virgin state, to the transaction of matters, by the sense especially whereby things divine are handled; whether (it be not) with a mind much more vigorous, with a heart much more alive, than when that whole habitation of our interior man, stuffed with meats, inundated with wines, fermenting for the purpose of excremental secretion, is already being turned into a premeditatory of privies, (a premeditatory) where, plainly, nothing is so proximately supersequent as the savouring of lasciviousness…
This principal species in the category of dietary restriction may already afford a prejudgment concerning the inferior operations of abstinence also, as being themselves too, in proportion to their measure, useful or necessary. For the exception of certain kinds from use of food is a partial fast. Let us therefore look into the question of the novelty or vanity of xerophagies, to see whether in them too we do not find an operation alike of most ancient as of most efficacious religion… I return likewise to Elijah. When the ravens had been wont to satisfy him with bread and flesh, why was it that afterwards, at Beersheba of Judea, that certain angel, after rousing him from sleep, offered him, beyond doubt, bread alone, and water? Had ravens been wanting, to feed him more liberally? Or had it been difficult to the angel to carry away from some pan of the banquet-room of the king some attendant with his amply-furnished waiter, and transfer him to Elijah, just as the breakfast of the reapers was carried into the den of lions and presented to Daniel in his hunger? But it behooved that an example should be set, teaching us that, at a time of pressure and persecution and whatsoever difficulty, we must live on xerophagies…. Anyhow, wherever abstinence from wine is either exacted by God or vowed by man, there let there be understood likewise a restriction of food fore-furnishing a formal type to drink. For the quality of the drink is correspondent to that of the eating. It is not probable that a man should sacrifice to God half his appetite; temperate in waters, and intemperate in meats….
The apostle reprobates likewise such as bid to abstain from meats; but he does so from the foresight of the Holy Spirit, precondemning already the heretics who would enjoin perpetual abstinence to the extent of destroying and despising the works of the Creator; such as I may find in the person of a Marcion, a Tatian, or a Jupiter, the Pythagorean heretic of today; not in the person of the Paraclete. For how limited is the extent of our interdiction of meats! Two weeks of xerophagies in the year (and not the whole of these — the Sabbaths, to wit, and the Lord's days, being excepted) we offer to God; abstaining from things which we do not reject, but defer.
For since, as I before said, there are various proclamations, listen, as in a figure, to the prophet blowing the trumpet; and further, having turned to the truth, be ready for the announcement of the trumpet, for he says, 'Blow the trumpet in Sion: sanctify a fast' This is a warning trumpet, and commands with great earnestness, that when we fast, we should hallow the fast. For not all those who call upon God, hallow God, since there are some who defile Him; yet not Him — that is impossible — but their own mind concerning Him; for He is holy, and has pleasure in the saints. And therefore the blessed Paul accuses those who dishonour God; 'Transgressors of the law dishonour God' So then, to make a separation from those who pollute the fast, he says here, 'sanctify a fast.' For many, crowding to the fast, pollute themselves in the thoughts of their hearts, sometimes by doing evil against their brethren, sometimes by daring to defraud…
We begin the holy fast on the fifth day of Pharmuthi (March 31), and adding to it according to the number of those six holy and great days, which are the symbol of the creation of this world, let us rest and cease (from fasting) on the tenth day of the same Pharmuthi (April 5), on the holy sabbath of the week. And when the first day of the holy week dawns and rises upon us, on the eleventh day of the same month (April 6), from which again we count all the seven weeks one by one, let us keep feast on the holy day of Pentecost — on that which was at one time to the Jews, typically, the feast of weeks, in which they granted forgiveness and settlement of debts; and indeed that day was one of deliverance in every respect.'
And concerning food let these be your ordinances, since in regard to meats also many stumble. For some deal indifferently with things offered to idols, while others discipline themselves, but condemn those that eat: and in different ways men's souls are defiled in the matter of meats, from ignorance of the useful reasons for eating and not eating. For we fast by abstaining from wine and flesh, not because we abhor them as abominations, but because we look for our reward; that having scorned things sensible, we may enjoy a spiritual and intellectual feast; and that having now sown in tears we may reap in joy in the world to come. Despise not therefore them that eat, and because of the weakness of their bodies partake of food.
You should therefore fast on the days of the passover, beginning from the second day of the week until the preparation, and the Sabbath, six days, making use of only bread, and salt, and herbs, and water for your drink; but do you abstain on these days from wine and flesh, for they are days of lamentation and not of feasting….
We enjoin you to fast every fourth day of the week, and every day of the preparation, and the surplusage of your fast bestow upon the needy; every Sabbath day excepting one, and every Lord's day, hold your solemn assemblies, and rejoice: for he will be guilty of sin who fasts on the Lord's day, being the day of the resurrection, or during the time of Pentecost, or, in general, who is sad on a festival day to the Lord. For on them we ought to rejoice, and not to mourn.
Yet even life in Paradise is an image of fasting, not only insofar as man, sharing the life of the Angels, attained to likeness with them through being contented with little, but also insofar as those things which human ingenuity subsequently invented had not yet been devised by those living in Paradise, be it the drinking of wine, the slaughter of animals, or whatever else befuddles the human mind. Since we did not fast, we fell from Paradise; let us, therefore, fast in order that we might return thither….
Do not, however, define the benefit that comes from fasting solely in terms of abstinence from foods. For true fasting consists in estrangement from vices. “Loose every burden of iniquity.” Forgive your neighbor the distress he causes you; forgive him his debts. “Fast not for quarrels and strifes.” You do not eat meat, but you devour your brother. You abstain from wine, but do not restrain yourself from insulting others. You wait until evening to eat, but waste your day in law courts. Woe to those who get drunk, but not from wine. Anger is inebriation of the soul, making it deranged, just as wine does. Grief is also a form of intoxication, one that submerges the intellect. Fear is another kind of drunkenness, when we have phobias regarding inappropriate objects; for Scripture says: “Rescue my soul from fear of the enemy.” And in general, every passion which causes mental derangement may justly be called drunkenness.
Fasting is the medicine of the soul, which teaches the body to abstain not only from vices but also from unnecessary desires. Just as the sick are often advised to abstain from certain foods, so too does the soul, wounded by sins, need the medicine of fasting, so that the allurements of pleasures may be removed and the purity of the heart may grow.
Thus, meat is to be avoided during fasts, for no sacrifice is pleasing if it nourishes the desires of the flesh. Likewise, wine must be tempered, lest the sweetness of drink weaken the fervor of devotion. For the holy Fathers abstained not only from food but also from drink, so that the entirety of body and soul might be consecrated to the Lord.
From this also arises the greater significance of fasting during Lent, so that not only is the external body afflicted, but the inner person is also renewed. For this reason, the number of forty days is sanctified, as the Lord fasted for forty days and nights in the desert and left this example for us, so that we may not falter in abstinence…
Fasting should not only be an abstinence from food but also a discipline of the soul. For one who abstains from food but does not abstain from sin harms himself more than he benefits. Thus fasting was pleasing to the holy men of old, as they neither consumed food nor committed sin. For it is written: 'Sanctify a fast' (Joel 2:15), meaning not only to observe a physical fast but also a spiritual one, free from sins, devoid of greed, unyielding to anger, and maintaining purity of mind and body.
As it is written, the fast is not broken before sunset, so that devotion is preserved throughout the entire day. For what benefit is fasting if the abstinence from food is not accompanied by discipline? The holy men of old fasted in such a way that the entire day was dedicated to prayer, and the fast itself became a pleasing sacrifice. This was also taught by the apostles, whose fasts combined not only abstinence from food but also persistent dedication to prayer.
For fasting alone is not enough; a virtuous life is also required. For what benefit is it to refrain from food if malice abounds? As the Lord said in the Gospel: "Do not be like the hypocrites, who appear gloomy" (Matt. 6:16). Fasting should be an internal sacrifice, so that not only is the body disciplined, but the soul is also purified.
The holy Fathers always observed this practice, ensuring that fasts were completed at evening time, reserving this period not only for abstinence but also for works of piety. After the day's labor, they devoted themselves to prayer and meditation on the divine law, for as evening approached, they offered a complete sacrifice of devotion to the Lord.
I speak not, indeed, of such a fast as most persons keep, but of real fasting; not merely an abstinence from meats; but from sins too. For the nature of a fast is such, that it does not suffice to deliver those who practise it, unless it be done according to a suitable law. For the wrestler, it is said, is not crowned unless he strive lawfully. To the end then, that when we have gone through the labour of fasting, we forfeit not the crown of fasting, we should understand how, and after what manner, it is necessary to conduct this business; since that Pharisee also fasted, but afterwards went down empty, and destitute of the fruit of fasting….
I have said these things, not that we may disparage fasting, but that we may honour fasting; for the honour of fasting consists not in abstinence from food, but in withdrawing from sinful practices; since he who limits his fasting only to an abstinence from meats, is one who especially disparages it. Do you fast? Give me proof of it by your works! Is it said by what kind of works? If you see a poor man, take pity on him! If you see in enemy, be reconciled to him! If you see a friend gaining honour, envy him not! If you see a handsome woman, pass her by! For let not the mouth only fast, but also the eye, and the ear, and the feet, and the hands, and all the members of our bodies.
And with respect to the two former precepts, we will discourse to you on another occasion; but we shall speak to you during the whole of the present week respecting oaths; thus beginning with the easier precept. For it is no labour at all to overcome the habit of swearing, if we would but apply a little endeavour, by reminding each other; by advising; by observing; and by requiring those who thus forget themselves, to render an account, and to pay the penalty. For what advantage shall we gain by abstinence from meats, if we do not also expel the evil habits of the soul? Lo, we have spent the whole of this day fasting; and in the evening we shall spread a table, not such as we did on yester-eve, but one of an altered and more solemn kind. Can any one of us then say that he has changed his life too this day; that he has altered his ill custom, as well as his food? Truly, I suppose not! Of what advantage then is our fasting? Wherefore I exhort, and I will not cease to exhort, that undertaking each precept separately, you should spend two or three days in the attainment of it; and just as there are some who rival one another in fasting, and show a marvellous emulation in it; (some indeed who spend two whole days without food; and others who, rejecting from their tables not only the use of wine, and of oil, but of every dish, and taking only bread and water, persevere in this practice during the whole of Lent); so, indeed, let us also contend mutually with one another in abolishing the frequency of oaths. For this is more useful than any fasting; this is more profitable than any austerity.
What need then is there to say more? Stand only near the man who fasts, and you will straightway partake of his good odour; for fasting is a spiritual perfume; and through the eyes, the tongue, and every part, it manifests the good disposition of the soul. I have said this, not for the purpose of condemning those who have dined, but that I may show the advantage of fasting. I do not, however, call mere abstinence from meats, fasting; but even before this, abstinence from sin; since he who, after he has taken a meal, has come hither with suitable sobriety, is not very far behind the man who fasts; even as he who continues fasting, if he does not give earnest and diligent heed to what is spoken, will derive no great benefit from his fast.
After you have paid the most careful attention to your thoughts, you must then put on the armour of fasting and sing with David: I chastened my soul with fasting, and I have eaten ashes like bread, and as for me when they troubled me my clothing was sackcloth. Eve was expelled from paradise because she had eaten of the forbidden fruit. Elijah on the other hand after forty days of fasting was carried in a fiery chariot into heaven. For forty days and forty nights Moses lived by the intimate converse which he had with God, thus proving in his own case the complete truth of the saying, man does not live by bread only but by every word that proceeds out of the mouth of the Lord. The Saviour of the world, who in His virtues and His mode of life has left us an example to follow, was, immediately after His baptism, taken up by the spirit that He might contend with the devil, and after crushing him and overthrowing him might deliver him to his disciples to trample under foot. For what says the apostle? God shall bruise Satan under your feet shortly. And yet after the Saviour had fasted forty days, it was through food that the old enemy laid a snare for him, saying, If you be the Son of God, command that these stones be made bread. Under the law, in the seventh month after the blowing of trumpets and on the tenth day of the month, a fast was proclaimed for the whole Jewish people, and that soul was cut off from among his people which on that day preferred self-indulgence to self-denial.…
I do not, however, lay on you as an obligation any extreme fasting or abnormal abstinence from food. Such practices soon break down weak constitutions and cause bodily sickness before they lay the foundations of a holy life. It is a maxim of the philosophers that virtues are means, and that all extremes are of the nature of vice; and it is in this sense that one of the seven wise men propounds the famous saw quoted in the comedy, In nothing too much. You must not go on fasting until your heart begins to throb and your breath to fail and you have to be supported or carried by others. No; while curbing the desires of the flesh, you must keep sufficient strength to read scripture, to sing psalms, and to observe vigils. For fasting is not a complete virtue in itself but only a foundation on which other virtues may be built. The same may be said of sanctification and of that chastity without which no man shall see the Lord. Each of these is a step on the upward way, yet none of them by itself will avail to win the virgin's crown. The gospel teaches us this in the parable of the wise and foolish virgins; the former of whom enter into the bridechamber of the bridegroom, while the latter are shut out from it because not having the oil of good works they allow their lamps to fail. This subject of fasting opens up a wide field in which I have often wandered myself, and many writers have devoted treatises to the subject. I must refer you to these if you wish to learn the advantages of self-restraint and on the other hand the evils of over-feeding.
The fasts before Easter will be found to be differently observed among different people. Those at Rome fast three successive weeks before Easter, excepting Saturdays and Sundays. Those in Illyrica and all over Greece and Alexandria observe a fast of six weeks, which they term "The forty days' fast." Others commencing their fast from the seventh week before Easter, and fasting three five days only, and that at intervals, yet call that time "The forty days' fast." It is indeed surprising to me that thus differing in the number of days, they should both give it one common appellation; but some assign one reason for it, and others another, according to their several fancies. One can see also a disagreement about the manner of abstinence from food, as well as about the number of days. Some wholly abstain from things that have life: others feed on fish only of all living creatures: many together with fish, eat fowl also, saying that according to Moses, these were likewise made out of the waters. Some abstain from eggs, and all kinds of fruits: others partake of dry bread only; still others eat not even this: while others having fasted till the ninth hour, afterwards take any sort of food without distinction. And among various nations there are other usages, for which innumerable reasons are assigned. Since however no one can produce a written command as an authority, it is evident that the apostles left each one to his own free will in the matter, to the end that each might perform what is good not by constraint or necessity. Such is the difference in the churches on the subject of fasts.
But [Bishop Cedd], desiring first to cleanse the place which he had received for the monastery from stain of former crimes, by prayer and fasting, and so to lay the foundations there, requested of the king that he would give him opportunity and leave to abide there for prayer all the time of Lent, which was at hand. All which days, except Sundays, he prolonged his fast till the evening, according to custom, and then took no other sustenance than a small piece of bread, one hen’s egg, and a little milk and water. This, he said, was the custom of those of whom he had learned the rule of regular discipline, first to consecrate to the Lord, by prayer and fasting, the places which they had newly received for building a monastery or a church.
To summarize my takeaways:
Early sources suggest fasting on Wednesday and Friday. Other sources introduce a Lenten fast, but the dates are a little unclear—sometimes just during Holy Week, sometimes just Good Friday and Holy Saturday, sometimes more.
There’s a mix: bread and water, bread and water and vegetables, or anything but meat and alcohol.
Often this isn’t mentioned at all, but sometimes it’s said that you shouldn’t eat anything until the evening.