213. Sex

There is a belief that men require more food than women; and if this refers only to total food consumption, it is true, because men weigh more generally, are more active physically, and perform more external work. It is not true, however, when we consider only the demands for the maintenance of what may be called physiological activity. Investigation shows that when the oxygen use of men and women of similar weight in a resting condition is compared, the gaseous exchange is practically the same.

Table XXXII. Energy Exchange (Oxygen Use) Of Men And Women In Resting State

1 " Metabolism and Practical Medicine," Von Noorden, Vol. I, pp. 260-261. 2 Loc. cit., p. 270.

Of course, when laboring the additional, oxygen consumption is proportional with both sexes to the work performed, and because man is in a general way of higher muscular development than woman, he uses a much larger total energy. It has been claimed that trained muscles, even when not in use, have greater metabolic activity than the untrained. The similarity of oxygen use, per unit of weight, by the two sexes does not sustain this conclusion.

214. Disposition

The temperament of an individual has much to do with his food requirements. Persons of a sanguine type, being more active, use more energy than the phlegmatic. Bodily movement, whether deliberate, or due to nervous activity, constitutes work, and must be sustained by an equivalent of energy derived either from food or body substance.

215. Work

All activity of the human body, whether in the maintenance of its functions or in the performance of labor, is work. The forcing of the blood through the arteries and veins, the digestion of food and its assimilation, we speak of as internal work, while walking, running, lifting, the use of tools, the moving about of various objects, and other forms of visible physical activity are designated as external work. The two formsof work may also be classified as physiological and mechanical. Nothing in nutrition is more important than the relation of food to work. This is true, not only because a larger proportion of the nutriment we take is expended in sustaining our external activities, but because we should understand the conditions bringing about an unnecessary expenditure of food energy. Indeed, outside of the storage of body substance, which amounts to but little except in the case of the young, all food energy goes to sustain work, either physiological or mechanical. In this connection, it is proposed to discuss only the relations of food to mechanical work.