St. Josemaria Escriva: Overeating is the forerunner of impurity.
Saint Asterius of Amasia: The strictness of the forty-day fast puts to death the passions, extinguishes anger and rage, cools and calms every agitation springing up from gluttony. And just as, in the summer, when the burning heat of the sun spreads over the earth, the northern wind gives a welcome blessing to those who are scorched, by dispersing the heat with a tender coolness, so fasting also provides the same by driving out of bodies the burning which is the result of overeating.
St. Jean-Baptiste de la Salle: It is so natural for people to seek pleasure in eating and drinking that Saint Paul, teaching early Christians to perform all their actions for the love and glory of God, is obliged to mention eating and drinking specifically, for it is difficult to eat without offending God. Most people eat like animals to satisfy their appetite.
St. John Climacus: If you have promised Christ to go by the strait and narrow way, restrain your stomach, because by pleasing and enlarging it, you break your contract. Attend and you will hear Him who says: "Spacious and broad is the way of the belly that leads to the perdition of fornication, and many there are who go in by it; because narrow is the gate and strait is the way of fasting that leads to the life of purity, and few there be that find it.
St. Paul (Philippians 3:17-19): Be followers of me brethren: and observe them that walk so as you have our form. For many walk whom often I told you of (and now weeping also I tell you) the enemies of the cross of Christ: Whose end is destruction: whose God is the belly: and their glory is in their confusion, who mind worldly things.
Pope St. Gregory the Great: As long as the vice of gluttony has a hold on a man, all that he has done valiantly is forfeited by him: and as long as the belly is unrestrained, all virtue comes to naught.
St. Maximos the Confessor: Love, self-restraint, contemplation and prayer accord with God's will, while gluttony, licentiousness and things that increase them pander to the flesh. That is why "they that are in the flesh cannot conform to God's will" (Rom. 8:8). But "they that are Christ's have crucified the flesh together with the passions and desires." (Gal. 5:24)
St. Nilus of Sinai: Why do demons wish to excite in us gluttony, fornication, greed, anger, rancor and other passions? So that the mind, under their weight, should be unable to pray as it ought; for when the passions of our irrational part begin to act, they prevent the mind from acting rationally.
St. Bernard of Clairvaux: Take even bread with moderation, lest a loaded stomach should make you weary of prayer.
St. Alphonsus Maria de Liguori: It is almost certain that excess in eating is the cause of almost all the diseases of the body, but its effects on the soul are even more disastrous.
St. Jean Marie Baptiste Vianney: He who lives in sin takes up the habits and the appearance of the beasts. The beast, which has not reason, knows nothing but its appetites. So the man who makes himself like the beasts loses his reason, and lets himself be guided by the inclinations of his body. He takes his pleasure in good eating and drinking, and in enjoying the vanities of the world, which pass away like the wind. I pity the poor wretches who run after that wind; they gain very little, they give a great deal for very little profit -- they give their eternity for the miserable smoke of the world.
St. John Climacus: Struggle with all your might against the stomach and restrain it with all sobriety. If you labour a little, the Lord will also soon work with you.
St. Alphonsus Maria de Liguori: Let us then take care not to be conquered by this brutal vice. St. Augustine says that food is necessary for the support of life; but, like medicine, it should be taken only through necessity. Intemperance is very injurious to the body as well as to the soul.
St. Maximos the Confessor: It is not food that is evil but gluttony, not the begetting of children but unchastity, not material things but avarice, not esteem but self-esteem. This being so, it is only the misuse of things that is evil, and such misuse occurs when the intellect fails to cultivate its natural powers.
St. John Cassian: I shall speak first about control of the stomach, the opposite to gluttony, and about how to fast and what and how much to eat. I shall say nothing on my own account, but only what I have received from the Holy Fathers. They have not given us only a single rule for fasting or a single standard and measure for eating, because not everyone has the same strength; age, illness or delicacy of body create differences. But they have given us all a single goal: to avoid over-eating and the filling of our bellies...A clear rule for self-control handed down by the Fathers is this: stop eating while still hungry and do not continue until you are satisfied.
St. Maximos the Confessor: Overeating and gluttony cause licentiousness. Avarice and self-esteem cause one to hate one's neighbor. Self-love, the mother of vices, is the cause of all these things.
St. Thalassios the Libyan: The thought of unchastity follows that of gluttony; of pride, that of self-esteem. The others all follow the three most common forms.
St. John Climacus: Know that often a devil settles in the belly, and does not let the man be satisfied, even though he has devoured a whole Egypt and drunk a River Nile. But after one has taken food, the unclean spirit goes away and sends against us the spirit of fornication, telling him our condition and saying, "Catch, catch, hound him; for when the stomach is full, he will not resist much.
Venerable Simeon, the New Theologian: Fasting is the mother of health; the friend of chastity; the partner of humblemindedness (illnesses are frequently born in many from a disorderly and irregular diet).
St. Jean Marie Baptiste Vianney: O my children! Let us no longer live for the pleasure of eating; let us live as the saints have done; let us mortify ourselves as they were mortified.
Venerable Louis of Granada, OP: Gluttony is an inordinate love of eating and drinking...When you feel the promptings of this shameful disorder, subdue them by the following considerations: Call to mind that it was a sin of gluttony which brought death into the world, and that it is the first and most important passion to be conquered, for upon the subjugation of this vice depends your victory over all others. We cannot successfully battle with enemies abroad when the forces within us are in a state of rebellion. Thus we see that the devil first tempted Our Saviour to gluttony, wishing to make himself master of the avenue through which all other vices find an easy entrance.