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DEMANDS OF THE BODY FOR NOURISHMENT. ia 
careful dietary studies, the composition of the food is deter- 
_ mined by analyzing samples of materials actually used. Again, 
a this method assumes that all the food is really consumed, 
4 whereas it is very plain that frequently no small portion is 
wasted in the kitchen or at the table. The difficulty is usually 
met in the later American studies, by measuring and compu- 
ting the amounts of nutrients in the waste and sometimes by 
analyzing samples of it. 
In preparing the results of dietary studies so that different 
studies may be compared, another difficulty appears. For ex- 
ample, in a family consisting of father, mother, and two chil- 
dren of different ages the amount of food taken by each is by 
no means the same, and it would be quite incorrect to divide 
the whole amounts consumed by four and call the result the 
amount used per person. Men, as a rule, eat more than 
women, women more than young children, and persons of 
active habits more'than those who take little muscular exer- 
cise. A coal heaver, who is constantly using up nutritive ma- 
terial or muscular tissue to supply the energy required for his 
severe muscular work, needs a diet with more protein and 
higher fuel value than a bookkeeper who sits at a desk all day. 
It is ordinarily estimated that, as compared with a man at 
moderate or light work, a woman under similar conditions 
- needs 0.8 as much food, and children amounts that vary with 

their ages, and such figures are used to reduce the statistics 
of a dietary to the standard of one man at moderate work. 
The various factors commonly used in the United States in 
computing the results of dietary studies are as follows: 
FACTORS USED IN CALCULATING MEALS CONSUMED IN DIETARY 
STUDIKS. . 
Man at hard muscular work requires 1.2 the food of a man at moderately ac- 
tive muscular work. 
- Man with light muscular work and boy 15-16 years old require 0.9 the food 
of a man at moderately active muscular work, 
Man at sedentary occupation, woman at moderately active work, boy 13-14, 
and girl 15-16 years old require 0.8 the food of a man at moderately active 
muscular work. 
Woman at light work, boy 12, and girl 13-14 years old require 0.7 the food 
of a man at moderately active muscular work. 
Boy ro-11 and girl ro—-12 years old require 0.6 the food of a man at moder- 
ately active muscular work. 
