Emphasis throughout this entire monograph has been laid upon the basal metabolism. We have not infrequently been taken to task by thoughtless critics of previous reports, who have maintained that the basal metabolism should be expressed only in periods of minutes or hours, and the length of time for which it should be expressed is determined solely by the length of the experimental period upon which the measurement is made. In the last analysis the basal metabolism of a given individual is the most important factor in his energy transformations for the 24 hours. If this is once known, the superimposed values for activities greater than lying are readily and with reasonable accuracy computed. It thus becomes of special interest to compute the probable daily caloric requirement of this group of men at the end of their diet test. For this purpose we have computed the values for the last 3 days and give the results in table 202. From this it can be seen that the basal heat per 24 hours was 1,367 calories. On these days there was an average gross intake of 2,486 calories. It has been found by Dr. T. M. Carpenter,1 of this Laboratory, in recent extensive research, that an average figure for the excess heat resulting from the ingestion of mixed diet is 6 per cent of the gross energy intake. This may be stated to be the "cost of digestion." Under these conditions 149 calories represents the "cost of digestion" for this period.

Table 202. - Calculation Of Probable Average Heat Output Per 24. Hours During Last Three Days Of Experiment - Squad A

aSee table 128.

bComputed from tables 46 to 58.

cBenedict and Carpenter, Carnegie Inst. Wash. Pub. No. 261, 1918, p. 343.

dComputed from table 194.

eIncrease in heat output above basal for exercise greater than walking and for sitting assumed to be 400 per cent and 10 per cent respectively. fComputed from daily records of walking (pedometer). gHeat output above basal per mile of level walking; computed from data in tables 142 and 128.

As outlined in previous sections, the basal metabolism assumes the individual to be lying down without food in the stomach. The extra heat due to the ingestion of food has already been accounted for as "cost of digestion." From the carefully kept records of these men, the number of hours during which they were sitting has been recorded and averages 11 hours for these 3 days. While many writers ascribe no value to the difference between lying and sitting positions, particularly if the subject be carefully adjusted in a steamer chair, it seems reasonable to consider 10 per cent as a probable factor for the increase in the metabolism, this being substantiated by a large amount of experimental evidence.2 The per hour figure for the basal value is 57 calories; 10 per cent of this value, multiplied by 11 hours, will therefore give 63 calories for the extra heat output due to the sitting position.

From the pedometer records these men showed an average mileage of 6.7 miles per day for the 3 days (January 30 and 31 and February 1). Extensive data on the energy requirements for horizontal walking, secured in the treadmill experiments (see p. 533) give accurate figures for computing the average caloric requirement for walking 1 mile. It has thus been found that the extra energy above basal for walking 1 mile would mean, at this stage of the diet restriction, 56 calories. This multiplied by the daily mileage of 6.7 miles equals 375 calories for the activity of walking.

In addition to the walking, the men reported on the average about 1 hour exercise more active than walking. With this factor we must make several rather debatable assumptions. An examination of the protocols shows that the men not infrequently included in this exercise certain of the simpler gymnastic exercises, such as were shown in the moving pictures, etc.; also other work which usually calls for severe work for short periods but relatively long periods of rest. These activities were recorded as work greater than walking. It seems to us reasonable to assume for this exercise an increased output of heat above basal amounting to 400 per cent. The basal value was 57 calories per hour; 400 per cent of this for 1 hour would therefore amount to 228 calories.

1Benedict and Carpenter, Carnegie Inat. Wash. Pub. No. 261, 1918, p. 343. 2Emmea and Riche, Am. Journ. Physiol., 1911, 27, p. 406; also Soderstrom, Meyer, and Du Bois, Arch. Intern. Med., 1916, 17, p. 872.

We thus have a total energy output, computed on this basis, of 2,182 calories. The element of greatest uncertainty in the whole computation is admittedly the last factor, namely, the energy due to exercise greater than walking. Possibly, also, the increase above basal due to the sitting should be somewhat greater than it is, for one can conceive of students giving off a very considerable amount of heat when sitting and gesticulating. A recent series of experiments at the Nutrition Laboratory with several groups of Simmons College students has shown that reading aloud has a strikingly small effect upon the quiet resting metabolism, so we are inclined to think that our figure of 10 per cent is not far from correct. A comparison of this total figure of 2,182 calories with the average net calories in the diet for these 3 days (2,245 calories) is of interest. This agreement is in all probability a fortuitous one, as it would assume a long-established body-weight, which previous discussion has shown was not actual, especially on these last few days. We introduce this method of calculation, however, in part to illustrate the great significance of an accurate knowledge of the 24-hour basal requirement as the foundation for computing the probable daily heat output.

From the gaseous-metabolism measurements, therefore, which show a profound reduction in the basal metabolism on the two different types of apparatus and from the dietetic intake as calculated from the net calories, it is clear that the energy requirements of these men were very much lower at the end of the experiment than they were at the beginning with normal diet. A computation of the probable dietetic requirements of these men during the last three days of the diet seems to substantiate fully the inferences drawn from the other criteria, and it is quite clear that these men were subsisting upon a diet fully one-third less than that normally required. The full significance of this, however, lies not so much in the fact that there was an actual reduction of one-third, but that it implies distinctly that there must have been a proportionately great reduction of the energy demands for work other than the basal maintenance. The results obtained in the treadmill experiments showed clearly that the energy for forward progression, i. e., the amount of energy required to move 1 kilogram 1 horizontal meter was appreciably lower when the men were on restricted diet than with normal diet. In connection with that discussion it was pointed out that although we could speak with certainty only of this particular type of muscular work, yet we have every reason to believe that the same efficiency of muscular coordination would obtain with other types of muscular work. This suggests a greatly lowered energy requirement for all of the activities of the day not merely in the lying position and post-absorptive condition, nor only when walking on the treadmill, but likewise in all the extraneous activities entering into the daily life.