In our study of variations in basal metabolism, special consideration has been given to the question of those factors which tend to lower the metabolism, and it was early recognized that prolonged fasting produced such an effect. The results obtained at the Nutrition Laboratory during the 31-day fasting experiment2 on the subject L. are decisive on this point. Here the analysis was first made upon the basis of per kilogram of body-weight and per square meter of body-surface; the body-surface was computed by the old formula of Meeh. By both methods of computation, definite loss in heat production was found as the fast progressed, save that after the fourteenth or fifteenth day there was a tendency to constancy. A subsequent revision of the calculations of body-surface, based upon a series of photographs and the more modern Du Bois measurements,3 confirmed the earlier findings and placed them upon a more scientific basis.

A somewhat complex factor entered into the interpretation of the values for the basal metabolism of this fasting man in that a definite acidosis developed. Although we believe that acidosis tends to stimulate the metabolism and thus would partly offset the depressing effect of the fasting per se, nevertheless there is no question but that the metabolism per kilogram of body-weight or per square meter of body-surface was distinctly lowered as a result of fasting. Of particular significance is the fact that with this fasting man there was no proportionate loss of strength but a general feeling of unimpaired mental and physical activity. While the subject showed a falling off in the dyna-mometric tests, from a superficial observation one would never realize that the man had been without food for 31 days. In talking to a group of medical men on the thirty-first day of his fast, he exhibited all the vivacity, strength of voice, and vigor of gesture that an ordinary individual would use. We thus have here evidence of a depressed metabolism unaccompanied by marked loss in intellectual or physical powers. It was demonstrated, therefore, that a specific factor, namely, complete inanition, can produce a definite and thoroughly established lowering of metabolism.

1 Benedict, Journ. Biol. Chem., 1915, 20, p. 299.

2 Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915.

3 Benedict, Am. Journ. Physiol., 1916, 41, p. 292.

The next evidence obtained in the Nutrition Laboratory of a pronounced decrease in the metabolism was the metabolic condition subsequent to the Allen fasting treatment for diabetes. In an extensive series of observations on metabolism in diabetes made in this Laboratory in conjunction with Dr. Elliott P. Joslin, cases of severe diabetes of the acid type showed high metabolism when compared with groups of normal individuals of like height and weight. After a few days' fasting under the remarkable Allen fasting treatment, the acidosis disappeared and the previously existing high metabolism was followed by a striking decrease in metabolism to far below that of the controls. This fall in the metabolism was found in so many cases that it may be considered as thoroughly established. It was subsequently verified by Du Bois in direct calorimetric observations. It may naturally be inferred that the cases of severe diabetes represent extreme emaciation or inanition, and hence it is appropriate to compare them with the man who fasted 31 days. From the diet charts of these patients after the Allen fasting treatment we find surprisingly low food-intakes. Yet these individuals are not moribund; they are able to be about the hospital, perform their own urinary tests, attend conferences, and engage in exercise even to the extent of walking 3 or 4 miles per day. While not rugged, they are by no means confined to bed, and yet they show this extraordinarily low basal metabolism. It appears, therefore, that with great loss of flesh there is a distinctly lower basal metabolism. We accordingly have here a second clear index of a lower metabolic level.

As a result of this long study of variations in basal metabolism and the factors which depress metabolism, we thus found a lower basal level only during fasting and with diabetics subsequent to the Allen fasting treatment. Since our earlier researches produced such negative results, it is incumbent upon us to examine previous studies interpreted as signifying a depressed metabolism due to undernutrition or other conditions and to present a critique of the results obtained.