As a matter of fact, basing such experiments on the weight of the average man - about 160 pounds - the energy requirements do amount to about 2200 calories, provided he is resting.

There must be great variations in the energy, and therefore food requirements. A man who is sick does not eat as much as a man who is well. A lumberman needs more calories than a clerk; an adult more than a child; a man usually more than a woman.

Let us take some concrete cases. Take the average man while sleeping. Sleeping does not suspend cellular activity. Oxidation of foodstuffs goes on, but not to the same extent as during the day, when the man is active. During every hour's sleep he expends about 65 calories. If he were to sleep twenty-four hours he would expend 1680 calories, but since he is a normal man and sleeps no more than about eight hours, he expends about 520 calories during this period. Let us take it that going and coming from work consumes two hours of the day. Walking is a light form of exercise requiring 170 calories per hour; two hours give us 340 calories. If the man is engaged in manual labor, as a carpenter perhaps, and works the "union" time of eight hours, he will need 240 calories per hour while so engaged; a total for the eight hours of 1920 calories. Our carpenter has six hours left for recreation - for reading newspapers and gossiping and seeing a "movie." We must count the recreation at a hundred calories per hour; a total then for six hours of 600 calories. Adding up our calories for the twenty-four-hour period, we get 520 + 340 + 1920 + 600 = 3380 as the total requirement per working day. You see, this is considerably above the 2200 calories that the average man needs when resting.

You may, with Tigerstedt, classify the requirements by the trade pursued. A shoemaker, he tells us, should thank the Lord when he gets the equivalent of 2400 calories, a weaver 2700, a farm laborer 4100, a lumberman over 5000.

Woman's Energy Requirements

Women need less. A seamstress rests satisfied - or should rest satisfied - with 1800 calories; a bookbinder with 2000; a servant with 2800; a washerwoman with 3200. Remember here that the average weight of woman is less than that of man; so that in proportion to the weight, the woman may receive just as many calories as man.*

Children

Children when one year old may need about 1100 calories. The increased requirements for each succeeding year are - very roughly - about 100 calories. Here again we encounter marked differences between the requirements of boys and those of girls. Where a girl of ten expends 1800 calories, a boy of that age may expend 2300.

* The phrase " getting so many calories" cannot, of course, be taken literally. From all that has been said in this chapter, we translate this oft-used expression to mean that amount of food which, when oxidized in the body, yields "so many calories."