The amount of food required by an individual will necessarily vary with the age, occupation, and temperament of the individual, and the climate in which he lives. However, by many series of experiments and studies of diets, certain definite standards of the amount of food needed under various conditions have been established and form a guide which may be profitably followed. The total food requirement for a given time is spoken of as a dietary.

The food must furnish the requisite amount of heat and energy needed by the body under various conditions, and also furnish material for growth of new cells and repair for those that are constantly breaking down.