STATE OF NUTRITION. 195 



approximately the maximum excretion. This would correspond to not 

 far from 100 grams of dry organic material, or about one-quarter 

 pound. In instances like these the body-weight is very rapidly re- 

 gained inside of 48 hours, showing that the large changes in body-weight 

 were chiefly due to fluctuations in water content of the body. 



With the average individual leading either a sedentary or a moder- 

 ately active life the same holds true, although in less degree. Frequent 

 weighing on delicate scales throughout a 24-hour day shows a, ten- 

 dency for the body-weight to fall, with recovery when food or drink is 

 taken, and sharp loss when urine or feces are passed.^ Hence fluctua- 

 tions in body-weight that appear from day to day have practically no 

 significance, and only the average weight for a week or more is of prac- 

 tical value. A progressive loss in weight extending over 7 or more days 

 indicates that drafts are being made upon organized body-tissue and 

 not simply upon the water content of the body. Failure to recognize 

 this fact has frequently led to erroneous assumptions regarding the 

 adequacy or inadequacy of a given diet. An individual may not 

 vary in body-weight or may even increase in weight and yet actu- 

 ally lose body-substance because of an inadequate diet. This can be 

 readily seen when we consider that with diets predominatingly carbo- 

 hydrate there is a strong tendency for the body to retain water, while 

 with diets predominatingly fat there is a distinct tendency for the 

 body to lose water.^ Under these circumstances the use of the body- 

 weight as an index of the adequacy of the fuel value of the diet is 

 open to grave criticism — a criticism that can be overcome only by 

 continuing the observation throughout several days, if not weeks. 



The fact that the large majority of adult individuals retain their 

 average body-weight constantly for long periods of time is, as stated, 

 yrima facie evidence of the adequacy of the diet from the fuel stand- 

 point, and a strong indication that the appetite instinctively adjusts 

 the intake to the needs. Accordingly, since there is this automatic 

 adjustment of intake to needs, we are primarily interested in the need 

 for fuel rather than in the actual food intake and are particularly inter- 

 ested in the fuel demands of the ordinary individual, what determines 

 them, and to what extent, if any, they may be decreased. In addition 

 to the abstractly scientific side of this problem we had at the tirae of 

 the investigation a question of tremendous and inmiediate national 

 importance, since any scientific study of the fuel needs of the body which 

 would contribute towards the solution of the possibihty of decreasing 

 the need for fuel required unmediate investigation. The fuel need of 

 the body may be considered from one point of view as that required 

 for the maintenance of vital activity at its lowest ebb under normal 



1 See Benedict and Joslin, Carnegie Inst. Wash. Pub. No. 176, 1912, fig. 1, p. 90. 



2 Benedict and Milner, U. S. Dept. Agr., Office Exp. Sta. Bull. 175, 1907, p. 225. Also cited 



by Benedict and Joslin, Carnegie Inst. Wash. Pub. No. 176, 1912, p. 92. 



