and efficient sources of energy for the human machine.

In the absence of butter some other form of fat is desirable in the diet,
because fat is so concentrated a food. There is a limit to the capacity of
the human stomach to hold food. People who live on a diet largely of rice,
which has almost no fat in its make-up, develop characteristically
distended abdomens, because they have to eat such a great quantity of food
to get fuel enough for their day's work. When people are for any reason
put on a milk diet for a considerable time it is customary to put
something into the milk to make it more concentrated, for otherwise they
would drink and drink and then hardly get fuel enough. To give a concrete
illustration--a man's energy requirement for a day may be met by from four
to five quarts of milk (unless he is doing very heavy manual labor), but
it would be much more practical to substitute a loaf of bread, which is
comparatively dry, for one quart of milk, and three ounces of fat (six
tablespoonfuls) for another quart of milk, making the total volume but
little over half what it would be if four quarts of milk were taken. For
people who are engaged in hard physical toil, fat is exceedingly important
for this purpose of gaining in concentration. "Fat is fuel for fighters,"
and it is perfectly reasonable to ask those who are not doing much heavy
labor to eat other kinds of food and save fat for those who simply have to
have it to do their work well. In the ordinary mixed diet one can easily
dispense with an ounce of fat (two tablespoonfuls). Each tablespoonful is
equalled in energy by an apple, or a banana, a large egg, two half-inch
slices of bread about three inches square, four dates, four prunes--and it
is no great strain on one's capacity for food to substitute such items for
the fat.

On account of its concentration, fat is good for transportation; and aside
from its energy value it gives the diet "staying" qualities. Other things
being equal, one feels hungry sooner after a meal without fat than after
one in which it is liberally supplied. People doing manual labor, and
especially out of doors, feel the pangs of hunger more than sedentary
folks and hence need more fat to keep them comfortable. No man can do his
best work when all the time thinking how hungry he is. It behooves us all
then, as good citizens, to recognize the greater need of our soldiers and
sailors and our hard-working laborers for as liberal allowance