Heat Output Per Square Meter Or Body-Surface With Low Diet, Squad A

A second popular method for comparing different individuals and the same individual under different conditions is on the basis of the heat production per square meter of body-surface. Employing the measurements of body-surface obtained by the Du Bois linear formula, which have been verified both by the height-weight chart and by the photographic method (see p. 241), we have to deal here with true body-surfaces rather than with the erroneous values computed by the formula of Meeh. The heat production per square meter of body-surface per 24 hours for each of the subjects has been computed for the days used in the previous comparison, i. e., October 1, November 24, and January 26, and recorded in table 130. With the heat production per kilogram of body-weight there were a number of instances in which there was no decrease as the experiment progressed and occasionally even slight increases. When the values for heat production at these periods are compared on the basis of per square meter of body-surface, we find no increase except with Kon, whose heat production increased from 836 to 846 calories. In one case, Vea, the decrease on January 26 was small. The most marked decreases were noted between October 1 and November 24, as would be expected, for the latter date represents a period when the body-weight was practically at a minimum. Between November 24 and January 26 there was relatively little change in weight.

Table 130. - Heat Per Square Meter Per 24 Hours (Computed From Individual Respiration Experiments) At Different Diet Levels - Squad A; Subjects Post-Absorptive And In Lying Position

1 See table 133 for explanation of period averages.

2 Minimum during sleep, after standard supper (700 calories) at restaurant from 6 to 12 hours before the experiment. Computed from values in table 131, for experiments on Sept. 29-30, Nov. 24-25, and Jan. 26-27.

When a comparison is made with the data in table 113 (see p. 493), it is seen that the values in table 130 are not abnormal, although they show a somewhat wide range from a minimum of 871 with Bro to a maximum of 1,027 with Mon, a range of 156 calories. On November 24 we find all the values were perceptibly lowered, with no values above 914 calories, this maximum value being for Mon. The minimum value for this date, 759 calories, instead of being with Bro as on October 1, is found with Vea, the greatest difference in the figures being 155 calories, or practically the same as on October 1. On January 26 the range is from the maximum of 897 to a minimum of 716, a variation of 181 calories, which is somewhat greater than that noted on October 1. Since the whole level was lowered on the average 152 calories, it can be seen that this range of 181 calories oh January 26 makes the actual percentage range larger than on the first day. Hence we may not infer that the restricted diet had a tendency to wipe out individual variations or deviations from the average. We note that while Mon shows the maximum heat output per square meter of body-surface per 24 hours for all three periods the minimum is represented on October 1 by Bro, on November 24 by Vea, and on January 26 by Pec. This implies, as was stated at the beginning in discussing the normality of these men, that the metabolism of Mon is distinctly on a higher level than that of the other men. It is also an interesting fact that the subject showing the next highest value on October 1 (Gar) is the third highest on November 24 and the fourth highest on January 26.

The average values for the entire squad show a continuous fall from 940 calories on October 1 to 817 calories on November 24 and 788 calories on January 26. The decrease between October 1 and January 26 is thus 16.2 per cent.

Attention is specially called to the fact that we have in the heat output per square meter of body-surface - a standard of measurement that supposedly levels all organisms from a mouse to an ox to the same physiological basis - a variation of 16 per cent with a group of 11 men between October 1 and January 26, a clear evidence of an absolute lowering of the heat per square meter of body-surface. Since the rectal temperature of these men remained essentially constant and, with one or two exceptions, the skin temperature was likewise constant, the significance of the body-surface law in this connection is hardly so great as one has been led to believe.

Group Measurement Of Basal Metabolism With Low Diet, Squad A

The successive metabolism measurements of Squad A in the group respiration chamber at intervals of approximately two weeks during the period of restricted diet have been recorded in table 131. Again emphasis must be laid upon the fact that the personnel of the squad through illness and other causes changed somewhat as the experiment continued. Hence the values for the total body-weight, total body-surface, and minimum carbon-dioxide production per hour can not be taken in a strictly comparative sense, and one should consider solely the values computed on the bases of heat production per kilogram per hour or per square meter per hour. These appear in the last two columns of the table.

The normal heat production, which was found on September 29-30 and has previously been recorded in table 114, is 1.10 calories per kilogram per hour and 40.8 calories per square meter per hour. The restricted diet began with breakfast on the morning of October 4. Approximately 10 days later (October 13-14), a second metabolism experiment showed a profound fall in the heat production to 1.02 calories per kilogram per hour and 37.6 calories per square meter per hour, a decrease of 7.3 per cent and 7.8 per cent, respectively. It so happens that these first two experiments represented values obtained with exactly the same personnel.

Table 131. - Minimum Metabolism During Sleep As Measured In Group Respiration Chamber - Squad A

1 Values represent 11 men only.

In the experiment on the night of October 27-28 but 11 men were in the squad. Hence there was a change in the total body-weight and body-surface and in the carbon-dioxide production. The heat production per kilogram of body-weight, however, is nearly identical with that obtained two weeks before, namely, 1.01 calories, but there was a decrease in the heat per square meter from 37.6 to 36.4 calories.

On November 10-11 the squad again consisted of 12 men and the heat production changed to 0.97 calorie per kilogram and 34.4 calories per square meter. These values remained essentially constant for the next four experiments, these being made on the nights of November 24-25, December 8-9, December 19-20, and January 12-13. It should be noted that beginning with December 19-20, the values are again for 11 men. On the night of January 26-27 another decided alteration was found in the heat production per kilogram of body-weight, which fell to 0.90 calorie, and in the heat production per square meter of body-surface, which fell to 31.8 calories. One week later, February 2-3, the metabolism was again slightly lowered, minimum values for the entire experiment being obtained of 0.89 calorie for the heat production per kilogram of body-weight and 31.4 calories for the heat production per square meter of body-surface.

It is evident that as a result of the restricted diet, the heat production of the squad has been lowered both per kilogram of body-weight and per square meter of body-surface. If we take the normal values found on September 29-30 as a basis of comparison, these values being controlled not only by the morning average metabolism measurements with the respiratory-valve apparatus (see table 113) but likewise by a duplicate set obtained with the same apparatus with Squad B on October 7, we find that the alteration in the heat production per kilogram of body-weight was from 1.10 to 0.89 calories per kilogram of body-weight, a fall of 19 per cent. On the basis of per square meter of body-surface we find a change from 40.8 calories on the night of September 29-30 - a value confirmed by those obtained with Squad B and likewise by the morning values secured with individual members of Squad A (see table 113) - to a value of 31.4 on the last night of the experiment, February 2-3, a decrease in metabolism per square meter of body-surface of 23 per cent.

From our experience in obtaining basal values with Squad B, however, it is not logical to assume that this decrease in the metabolism is due solely to the altered diet. With Squad B there was apparently a material seasonal fall in metabolism from October 7 to January 6, of 11 per cent per kilogram of body-weight, and 9 per cent per square meter of body-surface. (See discussion of table 114, page 497.) The decreases noted with Squad A are, however, so much greater than those found with Squad B that there is not the slightest doubt of a considerable alteration in the basal metabolism as a result of the diet restriction. The uncertain factor is the exact percentage to be ascribed to dietetic restriction and the exact percentage to be ascribed to the probable seasonal variation. Some hint as to the apportionment of these percentages may be obtained from an examination of the figures obtained with Squad B in the group respiration apparatus in the period of diet restriction. (See p. 523).