193. Minimum Nutrition

But after all, is minimum nutrition desirable? (The question of the desirable protein intake will be considered later.) Certainly much disease is caused by overeating. Many persons should practice greater moderation in satisfying their appetite. Those who take on excessive fat would do well to eat less, exercise freely, and thus draw upon the food for the maintenance of muscular activity, thereby preventing the storage of fat. It is especially true of those who live sedentary lives and store body substance beyond what may be regarded as a normal weight, that they would do well to be more abstemious. Doubtless by so doing in many cases bodily comfort would be promoted, the tendency to disease would be less, and mental efficiency would be increased. The case is different with that large number of persons who practically keep in nutritive equilibrium.

1Am. Jour. Phys., Vol. 16, p. 433.

194. Energy Requirement Determined By Energy Output

In discussing this we must constantly keep in mind the fundamental fact 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 loss of body substance. Stated another way, it is necessary to conclude that when the body is maintained in equilibrium, neither gaining or losing, there is an exact balance between the intake of available food energy and the expenditure of energy on the part of the organism. If an individual maintaining this balance is to continue a given energy expenditure and not lose flesh, he must continue to receive its food equivalent; or if he is to eat less food and not lose flesh, he must diminish the energy expenditure. The question is, then, can those of us who are active eat less, that is, can we effect a diminution in the necessary energy exchange of our bodies, and if we can, how is it to be done?

195. Reduction Of Energy Requirement

Of course, if the diet of any person is so light as to cause a loss of weight, then energy needs are diminished, because, other things being equal, the greater the body mass the greater the food needs. Moreover, when less food is eaten, the work of digestion is lowered. This is a minor factor, however. The most effective way of materially diminishing the work of the body is to restrict its muscular exertion; but with a person who continues a given occupation, it is scarcely possible for him to so modify his activities that his food needs are lowered to any appreciable extent. If a person undertook to restrict his daily and habitual movements, even though they might be purposeless, it would be at a sacrifice of comfort and with no certainty of its accruing to his physical advantage simply because it would be possible to eat less.

It is certain that a lower maintenance diet means, in general, a lower range of activity in some direction or other, unless we conclude that the human organism may be induced to take on new metabolic habits, with a larger net result of work accomplished in proportion to the food eaten. If we have confidence in the law of the conservation and correlation of energy, we must conclude that this cannot happen. It has been suggested that there is what may be called a race habit in the use of food. Doubtless this is so, but it would be absurd to expect that one race will accomplish more units of work with a given expenditure of energy than another. It may be true, however, that the racial habits of life or nervous temperament may so differ as to give one race preeminence in the proportion of food energy that is converted into productive work.

196. Relation Of Food And Body Type

One question has not been answered. We do not know what the effect on the physical type of man would be if generation after generation was to adopt food minima as a practice. If we reason by analogy, the results would not be desirable. Farm animals are not reared to their best estate or made most productive by studying to reduce their rations. We recognize the value of full-fed animals. It is fair to raise the question whether the full-fed man, with his reserve of energy is not the type upon which the virility, even the intellectual strength, of a nation must depend.