The ancient Cynic and Stoic philosophers were very interested in food.
“And indeed, at each meal there is not one hazard for going wrong, but many. First of all, the man who eats more than he ought to do wrong, and also the man who wallows in the pickles and sauces, and the man who prefers the sweeter foods to the more healthful ones, and the man who does not serve food of the same kind or amount to his guests as to himself.” – Musonius Rufus, Lecture XIIIB on Food 
They talk both about what we should eat and how we should eat it, if we want to live wisely and gain strength of character. For instance, we’re told of the Stoic teacher Musonius Rufus:
He often talked in a very forceful manner about food, on the grounds that food was not an insignificant topic and that what one eats has significant consequences. In particular, he thought that mastering one’s appetites for food and drink was the beginning of and basis for self-control.
Musonius taught that Stoics should prefer inexpensive foods that are easy to obtain and most nourishing and healthy for a human being to eat. It might seem like common sense to “eat healthy” but the Stoics also thought we potentially waste far too much time shopping for and preparing fancy meals when simple nutritious meals can often be easily prepared from a few readily available ingredients.
Musonius advises eating plants and grains rather than slaughtered animals. He recommends fruits and vegetables that do not require much cooking, as well as cheese, milk, and honeycombs. The Stoic weren’t strictly vegetarian — unlike their philosophical cousins the Pythagoreans. Some Stoics were probably vegetarian and others not, although they wouldn’t have eaten very much meat in general.
The Early Stoic and Cynic Diet
Zeno of Citium, the founder of the Stoic school, had for many years been a Cynic philosopher. “Zeno”, we’re told, “thought it best to avoid gourmet food, and he was adamant about this.” He believed that once we get used to eating fancy meals, we spoil our appetites and start to crave things that are expensive or difficult to obtain, losing the ability to properly enjoy simple, natural food and drink.
We know more about the Cynic diet because it was simpler and more austere. The Cynics were known, typically, for drinking water (instead of wine), and eating barley-bread and lentil soup or lupin beans — all very cheap ingredients. One Cynic letter says: “It is not only bread and water, and a bed of straw, and a rough cloak, that teach temperance…” We’re told of Crates, the Cynic teacher of Zeno, who abandoned his fortune:
Having adopted simpler ways, he was contented with a rough cloak, and barley-bread, and vegetables, without ever yearning for his former way of life or being unhappy with his present one.
The Stoics were generally more urbane and less extreme than their Cynic predecessors, and their diet seems to have been a bit less restricted. However, right down until the time of the last famous Stoic of antiquity, the Roman emperor Marcus Aurelius, we hear about some Stoics modelling themselves on the Cynic lifestyle, which in turn appears to have been influenced by aspects of the notorious Spartan agoge or training.
For example, in a letter to Marcus Aurelius, we find his rhetoric tutor and family friend, Marcus Cornelius Fronto, joking about how he saw one of the emperor’s little sons clutching a chunk of brown bread, “quite in keeping with a philosopher’s son.” In another letter, we get a glimpse of Marcus’ eating habits:
Then we went to luncheon. What do you think I ate? A wee bit of bread, though I saw others devouring beans, onions, and herrings full of roe.
Eating with Attention and Moderation
Musonius also thought we should train ourselves to avoid gluttony:
Since this behavior [gluttony] is very shameful, the opposite behavior — eating in an orderly and moderate way, and thereby demonstrating self-control — would be very good. Doing this, though, is not easy; it demands much care and training.
Stoics should eat slowly and with mindfulness of their own character and actions, paying attention (prosoche) to their thoughts and actions. They should use reason to judge where the boundary of what’s healthy lies and exercise moderation wisely.
The person who eats more than he should makes a mistake. So does the person who eats in a hurry, the person who is enthralled by gourmet food, the person who favors sweets over nutritious foods, and the person who does not share his food equally with his fellow-diners. […] Since these and other mistakes are connected with food, the person who wishes to be self-controlled must free himself of all of them and be subject to none. One way to become accustomed to this is to practice choosing food not for pleasure but for nourishment, not to please his palate but to strengthen his body.
That very simply means making an effort to eat healthy food. However, for Stoics the main reason for doing this isn’t just to improve our health, paradoxically, it’s to strengthen our character by exercising self-awareness and the virtue of self-discipline. That’s important today because we’re bombarded with contradictory advice about the healthiest way to eat. The Stoics would say that we shouldn’t allow that to confuse us. We should make a reasonable decision and stick to it in order to develop self-control because that’s fundamentally more important than losing weight or becoming physically healthy anyway. To be clear, both goals are of value, but for Stoics the primary goal is strength of character and physical health, while “preferred” as they phrase it, is of secondary importance.
Therefore, the goal of our eating should be staying alive rather than having pleasure — at least if we wish to follow the sound advice of Socrates, who said that many men live to eat, but that he ate to live. No right-thinking person will want to follow the masses and live to eat, as they do, in constant pursuit of gastronomic pleasures.
Many people who follow Stoicism today also employ intermittent fasting. It’s likely that some ancient Stoics did too. Socrates famously said that “hunger is the best relish”, alluding to the irony that we actually enjoy our food more when we’re hungry, and spoil our appetites when we over-indulge.
Please do not let this title alarm you and perturb your Stoic tranquility. Musonius Rufus (c. 20-30 AD – 101 AD), Epictetus’ revered teacher and mentor, would not have us counting calories, carbohydrates or any such thing. (Calories and carbohydrates would not be discovered until more than 1,700 years after his death, and even if he knew about them, he surely would have felt we have more important things to do) Indeed, I speak here of diet not in the sense of some exotic, time-limited food regimen designed to take off a few pounds, but diet in the sense the usual or habitual food and drink comprising one’s daily sustenance.
The Stoics saw philosophy as an art of living that should guide all of our human behaviors and seek to harmonize them with nature. As several of Musonius’s discourses on food, clothing, housing, and even shaving show, Stoicism was (and is) a practical philosophy for living a good life; therefore, even the most mundane and seemingly un-philosophical of topics make fitting grist for the Stoical mill.
What Has Food to Do with Philosophy?
A great deal, according to Musonius, who apparently spoke frequently and fervently on this topic that he considered no small matter for any philosopher. Musonius believed that habits of eating and drinking either build up or tear down the very foundation of the virtue of temperate self-control (sophrosyne, in the Greek). There’s an old adage advising would-be brides that “the way to a man’s heart is through his stomach.” For Musonius, the way to a man’s or a woman’s self-control is through his or her esophagus and stomach! “Indeed the throat was designed to be a passage of food, not an organ of pleasure, and the stomach was made for the same purpose as the root was created in plants. For just as the root nourishes the plant by taking food from without, so the stomach nourishes the plant by taking food and drink which are taken into it.”
Musonius devotes a two-part discourse (Discourses or Lectures 18A & 18B) several pages long to the topic of food, as preserved in a collection of, in essence, his post-lecture Q & A periods consisting of 21 discourses, or lectures, collected by a contemporary of his named Lucius and extracted in the fifth century AD by the Greek Joanne Stobaeus. He gives several specific dietary recommendations, including a diet based on vegetables and grains and limited in meat (which he considered a heavy food, the digestion of which “darken the soul” and slow down our thinking abilities. As for a summary in Musonius’ own (translated) words:
To sum up the question of food, I maintain that its purpose should be to produce health and strength, that one should for that purpose eat only that which requires no great outlay, and finally that at table one should have regard for a fitting decorum and moderation, and most of all should be superior to the common vices of filth and greedy haste.
Musonius Rufus Guts Gluttony before the Medieval Church Fathers
Musonius’ sage advice on the proper attitude and behavior toward food presages in many ways the advice of the Christian who five centuries later popularized the famous list of the “seven deadly sins,” Pope St. Gregory the Great (c. 540-604 AD). Gregory, in his Moralia on the Book of Job, listed seven deadly sins: gluttony, lust, greed, envy, sloth, and vainglory. When St. Gregory, and later St. Thomas Aquinas, expounded upon the varieties of the sin of gluttony, they defined gluttony as an inordinate or irrational desire for food and described dangers of eating too much food, too-expensive food, too-daintily-prepared food, and of eating too quickly or eating too often. In the 13th century, St. Thomas cited an old medieval verse that summed up the various forms in which gluttonous behaviors are expressed: “hastily, sumptuously, too much, greedily, daintily.”
We find these concerns in Musonius’ back in the first century AD eighteenth lecture as well. He warns of the gluttony of eating more than we should; of eating luxurious, gourmet foods, indeed, of “wallowing in the pickles and sauces”; of being a picky eater; of preferring sweet foods to healthy ones; of eating greedily and at “unseasonable times.” He minces no words, and warns us that gluttony makes us more like pigs or dogs than rational human beings. He advises us to train ourselves to appreciate simple foods. Indeed, he lauds the example of the Spartan, who, upon seeing some finicky man refuse to eat an expensive bird, declared, “I could eat a vulture or a buzzard.”
And here is where our great Stoic philosopher and our great medieval Catholic theologians share an even more important common ground on gluttony. St. John Cassian (360-435 AD), Eastern desert monk turned abbot in Marseilles, France, wrote in his Conferences about eight vices. Now vices are essentially bad habits, dispositions, or tendencies, the opposite of the good habits that are the virtues. Cassian’s list, echoing an even earlier list of eight “disturbing” or “assailing” thoughts expounded by desert monk Evagrius of Pontus (345-399 AD), would later be adapted a bit by Gregory and Thomas, as noted above, and become widely known as the seven capital vices (and even more widely known as the seven deadly sins – sins being acts of vice, literally vicious acts.) The connection with Musonius here is not so much this list of bad thoughts, vices, or sins, but the way in which they interact. Hear Cassian on this point:
Although these eight vices, then, have different origins and varying operations, yet the first six — namely, gluttony, fornication, avarice, anger, sadness, and acedia (anxiety, or weariness of the heart) — are connected among themselves by a certain affinity and, so to speak, interlinking, such that the overflow of the previous one serves as the start of the next one. For from an excess of gluttony there inevitably springs fornication; from fornication, avarice; from avarice, anger; from anger, sadness; and from sadness, acedia. Therefore these must be fought against in a similar way and by the same method, and we must always attack the ones that follow by beginning with those that come before. For a tree whose width and height are harmful will more easily wither up if the roots which support it are exposed and cut beforehand, and pestilential waters will dry up when their rising source and rushing streams have been stopped up with skillful labor.
Note then how these vices act in a sense like eight deadly dominoes, each on setting up the man in its thrall to fall into the next one.
Later, Gregory would state in his Moralia that “unless we tame the enemy dwelling within us, namely, our gluttonous appetite, we have not even stood up to engage in the spiritual combat.”
Musonius Rufus, 500 years before Gregory, (and 300 before Cassian) also saw gluttony as a gateway sin of sorts. The temptations of gluttony are before us every day, and if our powers of self-control are eroded through gluttony they will not rise to the challenge in other more important areas of our lives.
Although there are many pleasures which persuade human beings to do wrong and compel them to act against their own interests, the pleasure connected with food is undoubtedly the most difficult of all pleasures to combat. We encounter the other sources of pleasure less often, and we can therefore refrain from indulging in some of them for months or even years. But we will necessarily be tempted by gastronomic pleasures daily or even twice daily, inasmuch as it is impossible for a human being to live without eating. Consequently, the more often we are tempted by gastronomic pleasure, the greater the danger it presents.
For the great Catholic theologians, gluttony is a turning-away from the true good of God for the sake of lesser goods that can do our bodies harm; and our foundational Roman Stoic held virtually the same view. He warns that some intemperate men “resemble pregnant women…they cannot tolerate ordinary food; they have ruined their digestive system.”
Citing Socrates before him, who said we should eat to live rather than live to eat, this is why Musonius counseled a moderate intake of simple, inexpensive, natural, healthy foods. No wonder Musonius explained in Discourse 11 that the best job for a philosopher was that of a farmer.
The Original “Mediterranean Diet”
It is always an interesting thing when modern scientific research “discovers” what ancient philosophers discovered long ago through ordinary experience examined by rigorous reasoning. The modern, so-called “Mediterranean Diet” is patterned after the kinds of foods and drinks traditionally consumed by the peoples of countries surrounding the Mediterranean Sea (like Greece and Italy, of course). The base of this diet’s pyramid is formed by a daily predominance of fresh fruits, vegetables, whole grains, nuts, beans, legumes, herbs, spices, and olive oil, with at least a few weekly servings of fish and other seafood, less frequent and moderate portions of eggs and dairy foods including yogurt, a very limited intake of meat and sweets, and the optional consumption of red wine in moderation.
The Mayo Clinic and many other respected medical sources tout this as one of the world’s healthiest diets for maintaining ideal bodyweight and reducing the risk of heart and other diseases. When U.S. World and News Report gathers nutritional experts to rank the world’s best and worst popular diets among dozens of contenders each year, the Mediterranean Diet comes in each year in the very top few.
Consider that the Mediterranean Diet and a so-called, “Musonius Rufus Diet” would be just about the same thing. Indeed, Musonius warns against food imported from distant lands and he notes that people who eat the normal, inexpensive foods of their own region are healthier and stronger than those who crave exotic foods not a part of the standard Mediterranean fare. He even declares that slaves and country people who eat such simple native foods are healthier, sicker less often, less fatigued by labors, work harder, and become stronger than their masters and people who live in the city.
On Enjoying the Banquet of Life
The Musonius Rufus Diet, then, is a diet of sensible moderation, of asking yourself how much you need rather than how much you desire, of appreciating simple, natural foods, and of gratitude toward God and table manners towards one’s fellows fitting to a being made in God’s image. It is a diet that builds both a temperate soul and a tempered body that will serve as the foundation for acquiring and expressing all of the virtues. As Musonius’ star student Epictetus would later advise us, comparing life itself to a banquet:
Remember, you must behave as you do at a banquet. Something is passed around and comes to you: reach out your hand politely and take some. It goes by; do not hold it back. It has not arrived yet: do no stretch out your desire out toward it but wait until it comes to you.