The Rule of Saint Benedict: Chapter 39

Yesterday we read about the Reader during meal times. We have previously mentioned that monks eat less food and that the sick, the elderly, and the children get more food than the other brothers. What then is the proper amount of food?


Chapter 39. THE PROPER AMOUNT OF FOOD

1. For the daily meals, whether at noon or in mid-afternoon, it is enough, we believe, to provide all tables with two kinds of cooked food because of individual weaknesses. 
2. In this way, the person who may not be able to eat one kind of food may partake of the other. 
3. Two kinds of cooked food, therefore, should suffice for all the brothers, and if fruit or fresh vegetables are available, a third dish may also be added. 
4. A generous pound of bread is enough for a day whether for only one meal or for both dinner and supper.
5. In the latter case, the cellarer will set aside one-third of this pound and give it to the brothers at supper.
6. Should it happen that the work is heavier than usual, the abbot may decide― and he will have the authority― to grant something additional, provided that it is appropriate, 
7. and that above all overindulgence is avoided, lest a monk experience indigestion. 
8. For nothing is so inconsistent with the life of any Christian as overindulgence.
9. Our Lord says: Take care that your hearts are not weighed down with overindulgence (Luke 21:34)
10. Young boys should not receive the same amount as their elders, but less, since in all matters frugality is the rule. 
11. Let everyone, except the sick who are very weak, abstain entirely from eating the meat of four―footed animals.

This chapter is pretty self-explanatory. We see that two types of cook food are to be offered so those with allergies and what not have something else to eat. We then read that the abbot can make the decision to give extra food if the work was heavier than usual.

Then we see one of the best reasons for this rule on food; so that we may not overindulge ourselves. One reason being that overindulgence can cause indigestion, but another reason - and one I've stated many times - is because we are supposed to be learning to curb our passions. The Church has times throughout the year when we are supposed to fast; Wednesdays and Fridays, Lent, the Dormition Fast which we just finished, Nativity Fast, and a few others. Traditionally the strict fasts allowed for no meats, no dairy, no oils, and no fish - also, eating would be done usually one meal a day (usually the evening) on fasting days. Fasting is a discipline that the Church uses to help us learn how to curb our passions.

Fasting also partners with prayer, almsgiving and confession, readying the whole person like an athlete, body, mind, and soul, for an upcoming feast, similar to the way in which Orthodox Christians would hope to be properly prepared for the Second Coming. For this reason, during fasting seasons, no marriages should take place. Another important part of any fasting period is going to Confession. OrthodoxWiki

I encourage all of my readers to check out the rest of that link up there so they may better understand fasting.

If you do read more of that link then you'll see that fasting is not just about abstaining from food, but also from refraining from evil thoughts and actions. In this sense, we can see that living a monastic life is similar to living a life of permanent fasting as the monks give up so much in order to control their passions.