From the large mass of data that we have attempted to analyze in this report, certain very striking factors stand out above all others. While on the reduced diet these men underwent profound metabolic changes, which were indicated not simply by the losses in weight but also by alterations in pulse-rate, in blood pressure, to a slight extent in respiration rate, and more especially in the gaseous metabolism.

Cause For Depression In Metabolism

The depression in the total metabolism is, without doubt, the most prominent feature of the entire research, particularly as it was accompanied by a depression in other physiological factors, such as blood pressure and pulse-rate. Loewy and Zuntz1 also noted a lowered metabolism and give two possible explanations of it. One was that the depression may have been wholly due to a lowered protein intake, the other that there may have been a very considerable decrease in the active cell-substance. The first of these two hypotheses they dismiss, because Loewy, from the nitrogen excretion of the urine, showed that he was living upon a distinctly high nitrogen level. The explanation of Loewy and Zuntz thus rests solely upon the hypothesis that there was a considerable loss of active cell-substance, and they conclude that when the protein content of the diet is large and the caloric intake is insufficient it is impossible to prevent the disintegration of active body-substance. None of our men happened to have as high a nitrogen excretion as that of Loewy, but with some it was fairly large and with others fairly small. Consequently we do not believe that the protein intake of itself played any particular r61e in this case. Loewy and Zuntz naturally lacked demonstration of the loss of protein from the body.

One of the possible explanations of this lowered metabolism is that with a weight-loss there is less work for the musculature to perform in its ordinary activities - less weight to be lifted and less weight to be moved. This may even apply in the case of respiratory and heart muscles. A lower metabolism as a result of reducing the load to be moved would therefore be expected.

A second possible explanation is that with the reduction in diet, and consequent loss of body-weight, there may be a removal of fat from the tissues of the cells that makes the muscles somewhat more flexible, capable of more severe work and greater efficiency. This is perhaps in part comparable to a certain phase of athletic training, which combines the removal of fat by excessive activity with the enlargement of the muscles with practice. Comments made in gymnasium classes implied that the men found the muscles were more free when they were on the reduced diet than when they were on uncontrolled diet.

1Loewy and Zuntz, Berl. klin. Wochenschr., 1916, 53, p. 825. As this monograph goes into page proof, our attention has been called to a second article by these authors (Zuntz and Loewy, Weitere Untersuchungen uber den Einfluss der Kriegskost auf den Stoffwechsel, Biochem. Zeitschr., 1918, 90, p. 244), cited in an editorial in the Journ. Am. Med. Assoc, 1919, 72, p. 574. We are not able to see the original article and in any event it is too late for its analysis in this report.

Since, however, the changes in the metabolism were accompanied in practically all cases by a large loss of nitrogen from the body, the correlation of the nitrogen loss with the lowered metabolism is a natural procedure. With Squad B the general picture is much the same as with Squad A, although as the weight loss and the nitrogen loss were only about one-half those of Squad A, the depressions are not so sharply accentuated as with that squad.

An inspection of the nitrogen figures leads us to believe, however, that the most obvious cause for this lower metabolism is the removal of some 175 or more grams of nitrogen from the bodies of these men, resulting in a withdrawal from the fluids bathing the cells of a large amount of nitrogenous material. This material, which acts as a stimulus to cellular activity, is probably of an acid nature. It is clear that a careful chemical analysis of the blood should have been made.

It is of prime importance to note that in this whole series of experiments with the 25 or more men involved, the picture exhibited by the individual men is almost identical with that shown by the group as a whole. In other words, we have here no exceptions. It is extremely unfortunate that all of the initial members of Squad A could not have completed the 4 months' test. This would have greatly simplified the averaging of the results. Of the original members of Squad A, however, there were 9 men who went through the entire period without a break; we have therefore averaged the values for the most important findings for these 9 men and present these averages in the form of a chart. (See fig. 124.) It should be emphasized at this point that our basal tables and our derived tables for the several factors studied are made up from an analysis of the situation as presented by all the members of both squads, and the conclusions are drawn from these figures. The curves given in this chart, however, are drawn from the picture presented by only 9 members of Squad A I So far as we can see, there is little, if any, change in the general appearance of the picture or the interpretation of the data as a result of this curtailment in the number of men. For a general picture showing the influence of low diet upon all the physiological factors mentioned, a chart is preeminently desirable, but in making such a chart it is necessary to average values in so far as possible for the same number of individuals. The body-weight curve, representing a composite curve of the weight changes of 9 men, has a particular interest in that the distinctive features brought out in discussing the individual body-weight curves, namely, the post-Sunday rises and the post-Christmas rise, are all clearly shown in this curve. The striking increase in body-weight following the resumption of normal diet is also prominent.

1The 9 men whose data were used for the chart in figure 124 are as follows; Bro, Can, Oar, Qui, Mon, Moy, Pea, Pee, and Vea.