356 



NATURE 



[July 4, 191; 



sumcd and carljon dioxide produced, the basal heat 

 output could be computed by indirect calorimetry, thus 

 furnishing the second index of metabolic level. The 

 pulse-rate was recorded simultaneously every morning. 

 Every other Saturday night the entire group of rnen 

 was taken to Bostonand placed inside a large respira- 

 tion chamber, where the men could sleep comfortably. 

 The carbon dioxide excretion of the twelve men was 

 thus determined simultaneously during deep sleep. 

 This furnished a third criterion for judging the meta- 

 bolic level. 



The control squad showed no seasonal variation, 

 and their basal metabolism, as measured in the large 

 respiration chamber in Boston, was found to be abso- 

 lutely identical with that of the first group of twelve 

 men prior to the restriction in diet. To check the 

 important findings with the first squad during the 

 early period of the investigation, the second squad 

 was later placed upon a very restricted diet for a 

 period of three weeks, the diet given being less than 

 one-half of their normal requirements. 



For both squads, when on diet, the food for each 

 day was carefully weighed, sampled, and analysed for 

 the individual men. It is thus possible for us to 

 measure the complete intake of protein and calories. 



The most important scientific findings may be 

 summed up as follows : — 



(i) A gradual reduction in weight to a point 12 per 

 cent, below the initial weight took place during a 

 period of from three to ten weeks, with low calories 

 and a moderate amount of protein in the food intake. 

 The normal demand of the men prior to the dietetic 

 alteration ranged from 3200 to 3600 net calories. One 

 squad of twelve men subsisted for three weeks on 

 1400 net calories without special disturbance. 



(2) After the loss in weight of 12 per cent, had been 

 reached, the net calories required to maintain this 

 weight averaged about 2300, or approximately one- 

 third less than the original amount required. 



(3) At the end of the reduction in weight the actual 

 heat output during the hours of sleep, as computed 

 by indirect calorimetry, was approximately one-fourth 

 less than normal, thus giving a rough confirmation 

 of the lowered number of calories found by actual 

 measurement of the food intake. That there was no 

 seasonal variation in metabolism was shown by 



■ the constancy in the metabolic level of the control 

 squad. 



(4) The heat output by indirect calorimetry per kilo- 

 gram of body-weight and per square metre of body- 

 surface v^'as essentially 18 per cent, lower than at the 

 beginning of the study. 



(5) Throughout the period of loss in weight, and 

 for some time afterwards, there was a marked 

 loss of nitrogen to the body. In round numbers 

 these men each lost approximately 150 grams 

 of nitrogen. There is an intimate relationship 

 between this "surplus nitrogen and the metabolic 

 level. Removing the " surplus nitrogen," we believe, 

 distinctly lowers the stimulus to cellular activity. 



(6) The nitrogen output per dav at the maintenance 

 diet of 2300 net calories was about 9 grams. The con- 

 trol group of twelve men, living substantially the san>e 

 life and eating in the same dining-room, but with un- 

 restricted diet, showed a nitrogen output of 16 to 

 17 grams per day. 



(7) The pulse-rate was astonishingly lowered. Many 

 of the men showed morning pulse-rates as low as 33, 

 and daily counts of 32, 31, and 30 were obtained; at 

 least one subject gave six definite counts on one 

 morning of 29. 



(8) The blood-pressure, both systolic and diastolic, 

 was distinctly lowered. 



(9) The skin temperature, as measured on the sur- 

 face of the hands and forehead, was with some sub- 



NO. 2540, VOL. lOl] 



jects considerably lower than normal. With most of 

 the men normal temperatures prevailed. 



(10) The rectal temperature was practically normal. 



My colleague. Dr. Walter R. Miles, found as a 

 result of numerous tests of the neuro-muscular pro- 

 cesses that there was no material change as a result 

 of the reduced diet. There was a very slight falling-bff 

 in the strength tests with the hand dynamometer. 



As one of the best indices of muscular performance, 

 my associate, Dr. H. Monmouth Smith, measured the 

 energy required by each man to walk one mile in 

 about twenty minutes. With a reduced diet the re- 

 quy-ement was found to be lower with all the men 

 than, with a normal diet, this being due, in part, to 

 the fact that the reduced weight' meant a lower weight 

 to transport. In other words, these men walked a mile 

 with noticeably less energy consumption than a man 

 not subsisting on a reduced diet. 



The subjective impressions were almost viniform 

 that the muscles in the thigh were distinctly weakened. 

 The men complained of difficulty in walking upstairs, 

 but our personal observations go a long way towards 

 refuting this, for all the men seemed able to go up- 

 stairs two steps at a jump on several occasions. On 

 February i, 1918, at Springfield, after four months 

 on diet, eleven of the diet squad were pitted against 

 eleven men from the college body in an arm-holding 

 contest for endurance. The arms were held extended; 

 palms down, at the level of the shoulder. The number 

 of men falling out was practically the same in both 

 squads ; as a matter of fact, seven in the diet squad 

 and eight in the uncontrolled squad held their arms 

 out for one full hour. 



The most noticeable discomfort experienced by the 

 subjects was a feeling of cold, which it is only fair 

 to say might be due in large part to the severity of 

 the past winter. In general, notwithstanding the very 

 great reduction in the metabolism, which we believe 

 was due to the removal from the body of the stimulus 

 to cellular activity of approximately 150 grams of 

 "surplus nitrogen," the whole period of lowered food 

 intake had no untoward effect upon the physical or 

 mental activities, and the men were able to continue 

 successfully their college duties. 



When the second squad was put upon a restricted 

 diet the picture exhibited by the first squad was 

 strikingly duplicated in all details, although A?, the 

 loss in weight was obviously not so great with the 

 second squad (6 per cent, as compared with 12 per 

 cent.) the phenomena were quantitatively somewhat 

 less emphasised. 



At the conclusion of the entire research the men 

 presented an appearance not unlike the average col- 

 lege student ; it would have been difficult to pick them 

 out from the rest of the college body on the campus. 

 On close inspection the members of the diet squad 

 would perhaps have appeared somewhat emaciated, 

 particularly in the face, but they were performing their 

 duties as college students, both physically and intel- 

 lectually, with no obvious reduction in stamina. 



The great objection to making practical deductions 

 from laboratory experiments is usually that such re- 

 searches are carried out on the lower animals, or if 

 men are studied, but one, or at the most two, are 

 used. With a group of twenty-four men, such as was 

 studied in this research, one is justified, if ever, vn 

 drawing deductions or making recommendations. W^ 

 cannot then be charged with faddism or irrational 

 propaganda if we are led to make certain definite 

 recommendations^recommendations that admittedly 

 we would never make in peace times, and that ad- 

 mittedly mav have serious faults. These recommenda- 

 tions are primarily a war measure. 



I find myself in a novel situation as a public advo- 

 cate of far-reaching dietetic alterations. Recalling my 



