For many years the Nutrition Laboratory has been studying the possibility of variations in nutritional levels, searching more especially for individuals or classes of individuals with a noticeably low metabolism. To this end evidence has been sought in experiments with a man having but one lung; with individuals claiming to subsist upon considerably less food than an ordinary individual; with vegetarians; with a man fasting for a period of 31 days; and with diabetic patients undergoing the Allen fasting treatment and subsequent low diet. None of these researches, however, gave definite evidence of a low metabolism except those carried out under the somewhat abnormal conditions of a complete fast and severe diabetes.

While the regular accumulation of experimental data regarding basal metabolism has proceeded unabated, the establishment or the discovery of subnormal metabolism was less accentuated since only negative results had previously been obtained. Recently, however, international complications, causing great food stringency in different parts of the war region, have again called our attention to the problem of low metabolism and undernutrition.

The tremendous efforts of the Central Powers of Europe to withstand the food blockades of their opponents resulted in a most surprising development of food substitutes, many of these being prepared from materials formerly used for stock feeding. A complete economic system was thus developed to secure the proper distribution and rationing of the various food materials. Notwithstanding this use of unusual foodstuffs, the rations of the civilian population of Germany were severely curtailed. Most of the early information as to dietetic conditions in Germany, which can be considered as having scientific merit, was brought to this country by Professor Alonzo E. Taylor, formerly assigned to the United States embassy in Berlin. The statistical evidence which he secured in Berlin through his office, by the cooperation of Dr. E. Rost of the Gesundheitsamt and of Professor Rubner, and from innumerable ration cards, shows that the Central Powers as a whole were compelled, on account of war conditions, to adopt a materially lowered ration. This gigantic experiment proves conclusively that such changes are not only possible, but are not necessarily cataclysmic. They therefore challenge the scientific world for explanation.

As compensatory consequences of ration curtailment, only a general loss in body-weight is reasonably demonstrated. Statistically this hardly seems proportional to the diet curtailment, and evidence regarding a possible general reduction in physical activity is absent.

Furthermore, there is lacking that careful scientific balance which is necessary to demonstrate an actual lowering of the metabolism to compensate, in part at least, for the lower food-intake. It appeared to us that if the German civilian population had found it possible under war conditions to subsist on these low rations and had apparently adjusted themselves to an entirely new and heretofore practically unrecognized nutritional level, the scientific foundation for this change was certainly worthy of exact study. Furthermore, such research seemed especially timely, as the attention of a large number of American people was, in 1917, directed towards the conservation of food; it was accordingly important to analyze critically the factors that play the chief r61e in such conservation. Strenuous efforts had been made to reduce the consumption of certain food materials, such as sugar, wheat products, and animal products, by advocating the substitution of other materials, but one factor had previously been for the most part neglected, i. e., the possibility of a reduction in the amount of food consumed. The general problem of reducing the total food consumption quantitatively could not, however, be seriously considered by the laity. In view of the emergency confronting this nation in 1917, it was natural that the importance of food conservation should likewise occupy the minds of practically all physiologists. The question therefore arose with the Nutrition Laboratory: Is it possible by any dietetic regime to lower the total amount of food consumed and not at the same time disproportionately lower efficiency for either intellectual or muscular activity? In other words, is it possible to make a dietetic alteration of material moment which will still enable individuals to carry on their general activities, both intellectually and physically, as members of society, without appreciable detriment?

It has not been the custom of the Nutrition Laboratory to direct its researches primarily for economic and sociological purposes; yet in view of its long-continued study of people with a low intake of food and conceivably low metabolism, and the not remote possibility that America might be obliged to undergo privations similar to those in Germany, although probably in less degree, it seemed eminently fitting for the Laboratory to study a question so important from the standpoints of patriotism, economy, and physiology, as the effect upon the metabolism of a reduction in diet. The extensive research which is reported in this publication is, in the last analysis, a furthering of the initial problem studied by the Nutrition Laboratory, i. e., a search for conditions resulting in subnormal metabolism. It was planned in detail in the spring of 1917 and carried out during the winter of 1917-18 with a selected group of normal individuals whose body-weight was lowered as a result of quantitative reductions in their diet.

Before giving the details and discussing the results of this research, a general history will be given of the experimental work leading up to the present study, together with brief abstracts and a critique of the work of other investigators on metabolism with a low intake of food.