Plutarch's Rules for the Preservation of Health (22-23)

ZEUXIPPUS. Medicinal vomits and purges, which are the bitter reliefs of gluttony, are not to be attempted without great necessity. The manner of many is to fill themselves because they are empty, and again, because they are full, to empty themselves contrary to nature, being no less tormented with being full than being empty; or rather, they are troubled at their fulness, as being a hindrance of their appetite, and are always emptying themselves, that they may make room for new enjoyment. The damage in these cases is evident; for the body is disordered and torn by both these. It is an inconvenience that always attends a vomit, that it increases and gives nourishment to this insatiable humor. For it engenders hunger, as violent and turbulent as a roaring torrent, which continually annoys a man, and forces him to his meat, not like a natural appetite that calls for food, but rather like inflammation that calls for plasters and physic. Wherefore his pleasures are short and imperfect, and in the enjoyment are very furious and unquiet; upon which there come distentions, and affections of the pores, and retentions of the spirits, which will not wait for the natural evacuations, but run over the surface of the body, so that it is like an overloaded ship, where it is more necessary to throw something overboard than to take any thing more in. Those disturbances in our bellies which are caused by physic corrupt and consume our inward parts, and do rather increase our superfluous humors than bring them away; which is as if one that was troubled at the number of Greeks that inhabited the city, should call in the Arabians and Scythians.

ZEUXIPPUS. Some are so much mistaken that, in order that they may void their customary and natural superfluities, they take Cnidian-berries or scammony, or some other harsh and incongruous physic, which is more fit to be carried away by purge than it is able to purge us. It is best therefore by a moderate and regular diet to keep our body in order, so that it may command itself as to fulness or emptiness. If at any time there be a necessity, we may take a vomit, but without physic or much tampering, and such a one as will not cause any great disturbance, only enough to save us from indigestion by casting up gently what is superfluous. For as linen cloths, when they are washed with soap and nitre, are more worn out than when they are washed with water only, so physical vomits corrupt and destroy the body. If at any time we are costive, there is no medicine better than some sort of food which will purge you gently and with ease, the trial of which is familiar to all, and the use without any pain. But if it will not yield to those, we may drink water for some days, or fast, or take a clyster, rather than take any troublesome purging physic; which most men are inclined to do, like that sort of women which take things on purpose to miscarry, that they may be empty and begin afresh.

ZEUXIPPUS. But to be done with these, there are some on the other side who are too exact in enjoining themselves to periodical and set fasts, doing amiss in teaching nature to want coercion when there is no occasion for it, and making that abstinence necessary which is not so, and all this at times when nature requires her accustomed way of living. It is better to use those injunctions we lay upon our bodies with more freedom, even when we have no ill symptom or suspicion upon us; and so to order our diet (as has been said), that our bodies may be always obedient to any change, and not be enslaved or tied up to one manner of living, nor so exact in regarding the times, numbers, and periods of our actions. For it is a life neither safe, easy, politic, nor like a man, but more like the life of an oyster or the trunk of a tree, to live so without any variety, and in restraint as to our meat, abstinence, motion, and rest; casting ourselves into a gloomy, idle, solitary, unsociable, and inglorious way of living, far remote from the administration of the state, — at least (I may say) in my opinion.