Influence of food on metabolism

With the youngest children it was not possible to obtain ideal conditions for measuring the basal metabolism, i. e., complete muscular repose and with no food in the alimentary tract, or the "post-absorptive" condition. With adults the post-absorptive condition is usually not secured until 12 hours after an ordinary meal and the maximum increase following a protein-rich meal may be as high as 40 to 50 per cent for a short time, with its effect possibly continued even longer than 12 hours. With the children observed in this study, excessively large meals were not the rule, the last meal before the observations with the respiration apparatus being purposely considerably reduced.

A careful control of the muscular activity was secured through graphic records. With the youngest children, and especially the infants, however, it was not possible to obtain the required degree of muscular repose when there was no food in the stomach, because the want of food caused restlessness and frequently crying. In recognition of this difficulty, it was necessary to compromise by supplying as small an amount of food as would produce comfort and consequent muscular repose. This amount of food, even though small, inevitably influenced the metabolism. When older children were studied, it was possible to postpone the observations after a meal for a longer period of time, even for 4 or 5 hours. Accordingly, in the subsequent analysis of the metabolism data for the children of various ages, it must be remembered that as the age of the children increases the influence of the ingestion of food decreases correspondingly. The basal metabolism of children under 2 years of age can thus be compared with that of older children only on the distinct understanding that the values for the basal metabolism for the younger children are higher than they normally would be, owing to the influence of food.

The quantitative measurement of the influence of the ingestion of food upon the metabolism of infants should be given special study, such as has been done for adults in a previous publication from this laboratory. Certain more or less fragmentary evidence has, however, been accumulated in the present research with children, in part by design and in part by accident. With several of the children, a prolonged series of observations was made after food had been taken, some of these continuing 9 or 10 hours without interruption. The results of these observations give some information as to the possible influence of food. Here again we find a difficulty in interpretation in that the somewhat subtle influence of food is profoundly affected by a change in the activity; hence only periods of comparable muscular activity, or preferably muscular repose, can legitimately be used to determine the influence of food upon the metabolism. That is, it must be assured that the increase in the metabolism after food is not due to muscular activity before assuming it is due to the stimulus of food.