13 Dicæarchus in his book of Antiquities, describing Greece, relates that under Saturn, that is in the Golden Age, when the ground brought forth all things abundantly, no one ate flesh, but every one lived on field produce and fruits which the earth bore of itself. Xenophon in eight books narrates the life of Cyrus, King of the Persians, and asserts that they supported life on barley, cress, salt, and black bread. Both the aforesaid Xenophon, Theophrastus, and almost all the Greek writers testify to the frugal diet of the Spartans.
Chæremon the Stoic, a man of great eloquence, has a treatise on the life of the ancient priests of Egypt, who, he says, laid aside all worldly business and cares, and were ever in the temple, studying nature and the regulating causes of the heavenly bodies; they never had intercourse with women; they never from the time they began to devote themselves to the divine service set eyes on their kindred and relations, nor even saw their children; they always abstained from flesh and wine, on account of the light-headedness and dizziness which a small quantity of food caused, and especially to avoid the stimulation of the lustful appetite engendered by this meat and drink.
They seldom ate bread, that they might not load the stomach. And whenever they ate it, they mixed pounded hyssop with all that they took, so that the action of its warmth might diminish the weight of the heavier food. They used no oil except with vegetables, and then only in small quantities, to mitigate the unpalatable taste. What need, he says, to speak of birds, when they avoided even eggs and milk as flesh. The one, they said, was liquid flesh, the other was blood with the colour changed? Their bed was made of palm-leaves, called by them baiæ: a sloping footstool laid upon the ground served for a pillow, and they could go without food for two or three days. The humours of the body which arise from sedentary habits were dried up by reducing their diet to an extreme point.
Source: Against Jovinianus (New Advent)