Comparison Of Individual And Group Measurements Of Basal Metabolism With Low Diet, Squad A

Although the total heat production computed from the individual measurements of the gaseous metabolism in the morning experiments at Springfield with the respiratory-valve apparatus and the portable apparatus may not logically be compared with that computed from the results of the experiments with the group respiration chamber, since the personnel varied in the latter experiments, it is perfectly proper for us to compare the values for heat production on the two most commonly used bases, namely, per kilogram of body-weight and per square meter of body-surface. Using the data given in tables 129 and 130 and comparing them with those found on the corresponding nights with the group respiration chamber, we may determine the general trend of the metabolism by two entirely different methods. Such a comparison is made in table 132.

Table 132. - Comparison Of Measurements Of Metabolism With Different Diet Levels And Apparatus - Squad A. (Squad Averages Per 24 Hours.)

1 Averages from determinations on individual subjects who were in post-absorptive condition, and lying awake.

2 Computed from values on Sept. 29-30, Nov. 24-25, and Jan. 26-27, in table 131. 3 See table 133 (footnotes) for explanation of period averages.

4 (Normal values - Values at end of reduced diet) X100/Normal values.

Considering first the heat computed per kilogram of body-weight per 24 hours, we find that during normal diet, the value was slightly larger with the group chamber. At the period of minimum weight and at the end of the period with reduced diet the heat output was slightly lower with the group chamber. The percentage decrease from the beginning to the end of the experiment is also included in the able. With the individual measurements this was 11.5 per cent; with the group chamber it was 18.2 per cent. While the agreement is by no means perfect between these two methods of measurement, both give clear indications of a decided change even in the heat output per kilogram per 24 hours. When one considers that the experimental procedures differed in almost every detail, the agreement is perhaps as close as one could expect.

On the basis of body-surface area the records show that during normal diet a somewhat larger value was obtained with the group chamber, but at the minimum weight and at the end of the reduced diet the conditions are reversed. In any event the agreement between the two series is strikingly close, considering the wide differences in the methods of experimentation. The actual percentage decrease noted with the individual respiration apparatus was 16.2 per cent and with the group chamber 22.1 per cent. Thus, with both types of respiration apparatus, the evidence from this extensive series of experiments shows that the heat per kilogram of body-weight and heat per square meter of body-surface are greatly lowered, especially the latter.

A method of comparing the metabolism of these groups of individuals at different stages of their experiment which has a greater degree of scientific accuracy than the earlier methods previously discussed is to compare the basal metabolism as actually measured with that predicted by the Harris and Benedict formulae for individuals of like age, height, weight, and sex. Such a comparison has already been made for the normal data in table 113 and discussed in that connection. A further comparison should be made between the predicted values and the results of the metabolism measurements obtained during the period of minimum weight and at the end of the diet period. This is given in table 133, which shows both the absolute and percentile differences as found in the individual measurements with the respiratory-valve and the portable respiration apparatus. The differences between the normal and predicted values are also included in this table for reference. It is important to bear in mind that the predicted values are based upon a careful biometric analysis of the metabolism data obtained with a large number of individuals and are so adjusted as to give values with a reasonable degree of probability for individuals of the same height, weight, age, and sex.1

I Harris and Benedict, Carnegie but. Wash. Pub. No. 279, 1919.