To what extent the basal heat production may be increased as a result of carbohydrate ingestion may best be shown by considering the data in table 123. In this table the results are grouped according to the carbohydrates studied. The amounts ingested, the total length of observation, and the maximum increase above the basal value are here recorded. The length of time between the taking of the food and the maximum increase is also noted.

Unfortunately the calorimeter experiments are not sufficiently numerous, either as to the number of experiments with each carbohydrate or the number with the same amounts of food, to permit satisfactory comparisons of the relation of the individual carbohydrates to the maximum heat production. It is much to be regretted, also, that more experiments with pure carbohydrates were not made instead of with such mixed carbohydrates as bananas, popcorn, and rice. At the time these studies were made, however, the main purpose was to determine the possible maximum effect of carbohydrate ingestion upon the basal heat production. This is clearly established, as will be seen from the results given in the table. Although, with the possible exception of bananas and sugar, the evidence is not sufficiently complete to allow deductions as to the differences between the individual carbohydrates, the general picture is tolerably clear.

With sucrose it will be seen that the largest amount of heat was produced when the largest amount was ingested. This occurred in the experiment with A. H. M. on April 1, 1907, in which the period of experimenting was 8 hours, subdivided into four 2-hour periods. In this experiment an increment of 17 per cent was found in the period from 1/4 to 2 1/4 hours after food. A smaller amount of sugar taken by F. M. M. on January 31, 1910, produced an increment of but 11 per cent within one hour of taking the sugar, while a still smaller amount with A. TV. W. produced an increase of 8 per cent in approximately the same time. In all cases the maximum increment was found from 1/4 to 2 1/4 hours or even less after the ingestion of the carbohydrate.

Table 123. - Maximum Effect Of Carbohydrate Ingestion On Heat Production. (Calorimeter Experiments)

1The time given represents the experimental period. The food was usually taken less than half an hour before the beginning of the experiment. See tables 101 to 122 for details. 2Also juice of one lemon.

Unlike the experiments with sucrose, the maltose-dextrose experiments did not show the highest increment with the largest amount, as the greatest increase (28 per cent) was found with only 145 grams. The first two experiments recorded with the maltose-dextrose mixture are comparable in that the amounts of carbohydrate ingested are approximately the same and show an average increment of 13 to 14 per cent. In one of these experiments, that with Dr. R., the maximum effect was not observed until 4 1/4 to 6 1/4 hours after the food was taken. As this subject was particularly satisfactory from the standpoint of technique, we have no explanation for this long-delayed action in securing the maximum value. Two other experiments, which were made with approximately 300 grams of the sugar mixture, do not give very satisfactory duplicate results, as the value found with A. H. M. is more than twice as large as that found with A. L. L., although the time of appearance is practically the same, i. e., in the first 2 hours after food. In comparing the values in this group, it should be noted that in the calculation of the percentage increment the base-line used for J. J. C. was 1 hour, while that for the other subjects of the experiments with maltose-dextrose mixture was 2 hours.

The first three experiments with bananas and sugar are perfectly comparable in that practically the same amounts of bananas and sugar were given in each case. The increment is strikingly constant, varying only from 27 to 31 per cent. In the two experiments with A. L. L., the amounts ingested were approximately the same and reasonably concordant increments were obtained, i. e., 34 and 31 per cent respectively. With somewhat smaller amounts of bananas and sugar, J. J. C. gave an increment of but 26 per cent, while F. M. M., with an ingestion of 611 grams bananas and 9 grams of sugar, showed an increment of but 15 per cent.

In three experiments the ingestion of approximately 400 grams of bananas, without sugar, gave an increase in the heat production of 11 to 21 per cent, while in two experiments with popcorn a positive increment of 10 to 15 per cent was found. The experiment with boiled rice showed an increase of 6 per cent.

In considering these data it should be remembered that the results for the individual experiments can have but relatively little value, inasmuch as the amounts recorded for the greatest increments above basal requirements represent the observations in a single period and are thus liable to all the errors possible with such measurements. The emphasis should therefore be laid upon the general picture. The values given in this table show that it is perfectly possible for a pure sugar, such as sucrose, to increase the metabolism 17 per cent above the basal value; that a maltose-dextrose mixture can raise it somewhat higher; that bananas and sugar taken together give an increment of 15 to 34 per cent, depending upon the amount ingested; that bananas without sugar increase the heat production on the average 16 per cent; and that popcorn and rice may produce an increment of approximately 13 and 6 per cent respectively. In other words, it is very clear that large increments in the heat production may be expected from a practically protein-free diet. As these values deal only with the maximum periods, they simply show to what extent the basal value may actually be stimulated by the metabolic processes following the ingestion of pure or nearly pure carbohydrates.