The quantity of food required to maintain the body in vigour depends upon the following conditions:

1. External temperature. 2. Climate and season. 3. Clothing. 4. Occupation, work, and exercise. 5. The state of individual health. 6. Age. 7. Sex.

In civilised communities, where cooking is a fine art, the number and variety of food preparations is so great that the appetite is often stimulated beyond the requirements of the system, and consequently more food is eaten than is necessary or desirable to maintain the best standard of bodily health and vigour.

Persons in this country who live in comfortable circumstances often eat a dozen or fifteen ounces of solid food at breakfast, and again at luncheon, and perhaps thirty ounces more at dinner, making a total of, say, fifty-five or sixty ounces, to which are added only fifty or fifty-five ounces of fluids. This is about a third more than the amount of solids actually needed, forty ounces of solid food (which equals twenty-three ounces of water-free food) being a fair average for the daily necessities of most persons, one fourth of which should be animal and three fourths vegetable food. They eat too much and drink too little fluid in proportion. (See Water, p. 19).

Gluttony results in overdevelopment and overwork of the digestive apparatus. The stomach and bowels become enlarged, the liver is engorged, and a predisposition is established to degenerative changes, fatty heart, etc. (See Overeating).

The most northern Eskimos, for example, who often eat but one meal a day and then gorge themselves with tough meat, develop big jaws and distended abdomens (Cooke). Hayes described Eskimos who ate daily from twelve to fifteen pounds of food, about one third of which was fat, and the rest mostly meat; and Captain Hall, when on his arctic expedition, declares that he saw a native consume twenty pounds of raw meat and drink a quart of train oil within twenty-four hours.

It is stated by competent students of dietetics that more disease arises from abuse of food in regard to both quantity and quality than from abuse of drink.

Sir Henry Thompson says (Diet in Relation to Age and Activity): "More mischief in the form of actual disease, of impaired vigour, and of shortened life accrues to civilised man, so far as I have observed in our own country and throughout western and central Europe, from erroneous habits in eating than from the habitual use of alcoholic drink, considerable as I know the evil of that to be".

1. The external temperature increases the rate of oxidation processes in the body as it becomes colder by stimulating the respiration and circulation, and there is a consequent increased demand for food.

2. Climate and season influence the quantity of food eaten. Cold, bracing atmosphere stimulates the appetite, tempts one to exercise vigorously, and hence demands a larger consumption of fuel or food. A hot climate or season, with enervating, moist air, disposes man to languor and inactivity, and diminishes the appetite as well as the need for food.

3. Abundant clothing in a cold climate conserves the body heat, and less food is therefore required to maintain life than if the body is but scantily clad.

4. Exercise and muscular work also promote oxidation in the tissues and augment waste production from the muscles. This waste must be replaced, and energy must be supplied for work by additional consumption of food. Outdoor work demands more food than indoor work, and mental labour less than physical. Where men are fed upon a carefully regulated diet - as in prisons - it is" found that those who are performing hard labour require about one fifth more solid food than the others. The hard-labour prison dietary in England comprises fifty ounces of solid food, chiefly bread and vegetables. (See Diet in Prisons).

5. The state of health of the individual greatly modifies the amount of food required both indirectly, through influencing exercise and work, and directly, by the local condition of the digestive system.

Feeble and inactive persons may live on a third or less of the ordinary ration. Patients having chronic, purulent discharges, such as come from old sinuses, empyema, and tubercular abscesses, need large quantities of food - if they can digest it - to maintain their strength against the constant drain on their systems.

The nursing mother should have abundant food, for she must eat for two.

6. The age of the individual not only modifies the absolute amount of food required, but also the relative quantity in proportion to body weight. In the first year of life the infant grows six or eight inches, and at the end of a twelvemonth it should weigh two or three times as much again as at birth. This rapid growth necessitates a relatively larger consumption of food than at any other period of life, and hence the child is fed at first once every two hours, and later every three hours. During the second year the proportionate growth is half that of the first year, and during the third year it is one third that of the first. After the third year the weight and growth increase more uniformly, but the child must still have a large relative quantity of food, a great proportion of which must be tissue-forming - i. e., nitrogenous.

The following table is given by Prof. Arthur Goss (U. S. Department of Agriculture, Bulletin No. 54):

One meal of boy 14 to 16 years of age, inclusive, equivalent to 0.8 meal of man. One meal of girl 14 to 16 years of age, inclusive, equivalent to 0.7 meal of man. One meal of child 10 to 13 years of age, inclusive, equivalent to 0.6 meal of man. One meal of child 6 to 9 years of age, inclusive, equivalent to 0.5 meal of man. One meal of child 2 to 5 years of age, inclusive, equivalent to 0.4 meal of man. One meal of child under 2 years of age equivalent to 0.3 meal of man.

The rapidly growing, active boy often eats more animal food than the adult, and the middle-aged man eats more than the aged. A man of seventy years may preserve good health on a quantity of food which would soon starve his grandson.