Diet, δίαιτα, διαίτημα, diaeta , generally signifies an ordered manner of living , that is to say a controlled manner of consuming all that is indispensably necessary for animal life, whether in sickness or in health.

Thus diet consists not only in controlling the consumption of food and drink but also of the air in which one lives and of everything related: the location of place, climate, seasons [1]; to prescribe differing degrees of exercise and rest to follow, the timing and duration of sleep and wake; to determine the quality and quantity of matter which should be naturally evacuated from or retained within the body, and the positive effect of the passions, including the venereal act.

The doctrine formed from the combination of precepts which form diet is called dietetics , which prescribes the appropriate regime to be followed with respect to the things mentioned above, known according to the usage of [medical] schools as non-naturals . See Non-naturals.

This doctrine aims to preserve health in those who enjoy it, to protect from illnesses those who are threatened, and to cure those who are afflicted. The rules differ according to the temperament, age, sex, and time of year. They all aim to maintain the state of health by the same means by which it was established, and on the contrary to oppose the vices which tend to destroy it, or which have already done so.

The different goals of dietetics divide diet into three different types: the first is conserving, the second preserving, and the third curing. The first two belong to the part of Medicine called hygiene ; the third is one of its three branches called therapeutics . See Hygiene and Therapeutics.

Diet, in this sense, signifies in particular the regime prescribed to the sick with respect to food. The rules of this regime principally constituted the dietetics of ancient doctors, and nearly all the medicine of their time, because they employed few remedies. Having remarked that the all the assistance of nature and art ordinarily became useless if the sick abstained from food they had consumed while in health and had no recourse to a weaker and lighter food, they perceived the necessity of an art which indicated the foods appropriate for the sick and regulated their quantity, based on observations and reflections already made.

Hippocrates, who made diet his principal (and often only) remedy, had the first writing on the choice of regime: in what he left us on this subject, and particularly on the diet appropriate in ague diseases, we recognize the great master and consummate doctor more than in any of his other excellent works. See Regime.

It is also commonly meant by diet the abstinence kept by taking little or no food, thus to diet , not to eat or to eat very little and to make do with a small quantity of food, most often liquid. See Abstinence and Food.

All that relates to diet concerning food will be treated at length in various articles to which it will be appropriate to reference, especially in that of regime . See Regime.

Note

1. This environmental model derives from Hippocrates, Air, Water, Places .