258 Basal Metabolism in Men 



These results indicate. a rather wide variability in basal metabc 

 lism from individual to individual, even when heat production i 

 corrected for body size by expressing it in calories per kilo c 

 body weight or in calories per square meter of body surface area 



The problem now arises whether, under conditions such tha 

 the age factor 4 is practically eliminated, the basal metabolism c 

 the individual is essentially constant from day to day or whether i 

 shows sensible variations. In 1915 one of us 5 discussed the ques 

 tion of changes in the metabolism of the individual from day t 

 day, and showed that, contrary to the early assumption that th 

 basal metabolism of an individual remains essentially constan 

 from day to day, it is really variable. 6 



since there can be only one term minimum. The calories produced or th 

 volume of the gaseous exchange for any one of these periods which seems t 

 those acquainted with the technical details of the experiment reasonabl 

 free from experimental error, might serve as a measure of the metabolisn 

 Since, however, the basal metabolism of the individual can probably b 

 assumed to be sensibly constant for 1 day, it seems wisest to regard th 

 individual periods which appear the most free from possible experiment; 

 error as of the nature of duplicate, triplicate, etc. analyses, and to averag 

 these values. This daily mean has served as the unit in work at the Nutr 

 tion Laboratory. 



3 The frequency distributions of total calories and calories per squai 

 meter are shown in Figs. 1 and 2 of Harris and Benedict (Harris, J. A., an 

 Benedict, F. G., Scient. Month., 1919, viii, 388-389). 



4 The results of a previous study of the relationship between age an 

 metabolism (Harris and Benedict, 1 pp. 107-127) have shown that there 

 a gradual and practically linear decrease in metabolism with age durin 

 the period of adult life. The annual rate of decrease amounts to about 7.1 

 calories (per 24 hrs.) per year in men and 2.29 calories (per 24 hrs.) per ye 

 in women. Correction for body size by expressing the results in calorii 

 per kilo of weight gives a rate of decrease of 0.112 calorie in men and 0.15 

 calorie in women. If the results are expressed in calories per square meti 

 of body surface area as estimated by the Du Bois height-weight chart, tl 

 decrease for men is 3.60 calories and for women 2.96 calories per 24 hrs. &amp;lt; 

 life. The change due to age is not, therefore, large and cannot be assume 

 to be an important factor for subjects observed during a short period 

 time only. 



6 Benedict, F. G., J. Biol. Chem., 1915, xx, 290-295. 



6 This conclusion was based on a study of the difference between tl 

 highest and the lowest daily basal metabolism constant expressed as 

 percentage of the minimum value as a base. The study showed that t 

 differences varied greatly from subject to subject. In one case the ma: 

 mum and minimum oxygen consumption varied as widely as 31.3 per ce 



