Very strenuous exercise, like athletic contests and unnaturally slow movements, are both wasteful of food energy.
Again, a continuance of the same labor for hours, and a state of fatigue, whether it comes after a longer or shorter time, causes an increase in the energy expenditure per unit of work performed.
Economy in the use of energy that food supplies to the body is most fully secured when the movements of the body are at the natural rate; when periods of intense effort do not occur, and when the labor is not too long continued and is not carried to the point of fatigue.
Standard for Daily Dietaries (American)—Atwater.
| Protein. Grams. | Fuel value. Calories. | Nutritive ratio. | ||
| Woman with light muscular exercise | 90 | 2400 | 5.5 | |
| Woman with moderate muscular work | } | 100 | 2700 | 5.6 |
| Man without muscular work | ||||
| Man with light muscular work | 112 | 3000 | 5.5 | |
| Man with moderate muscular work | 125 | 3500 | 5.8 | |
| Man with hard muscular work. | 150 | 4500 | 6.3 |
The Relation of Food Economics to Social Welfare.—A virile nation is one whose citizens are of a good physical type, which means that they are well nourished. A well-fed people, other conditions being favorable, is a strong people. Food is the physical basis not only of the individual activity, but also of social energy. Any causes, therefore, which limit the food supply or increase the burden of securing adequate nourishment strike a blow at the nation’s vital power.
We must constantly keep in mind that the energy output is practically the energy requirement, under given conditions, of course; and the expenditure caused by the muscular activity of a particular individual cannot be reduced without affecting the work done or causing the loss of body substance.
Investigation has shown that there is a necessary daily protein minimum use. When insufficient protein is taken in the food, the necessary balance will be supplied by drawing on the tissues of the body. The food standards which are based on the observation of practice call for not less than 100 grams of protein daily for professional men and 175 grams for men at severe labor.
It is held to be significant that communities holding leading positions in the world consume a liberal amount of protein, or, conversely, that communities with an inferior physical and mental status use a low proportion of proteins in the diet. Again, if we argue from the analogies in feeding farm animals, generous protein feeding is desirable for the growth and maintenance of vigorous organisms and a satisfactory rate of production.
On the other hand, the well-known experience of the ages has shown that the poor who live on a low protein diet are the most liable to disease. It cannot be gainsaid that the meat eater has greater stamina and energy than the one whose diet is poor in protein.