foods, like peas and beans, not only satisfy the appetite, but supply
to the body abundant nourishment. Many immigrants live cheaply and
well with beans and bread as their main diet.

It is of vital importance that the relative value of different foods
as heat producers be known definitely; and just as the yard measures
length and the pound measures weight the calorie is used to measure
the amount of heat which a food is capable of furnishing to the body.
Our bodies are human machines, and, like all other machines, require
fuel for their maintenance. The fuel supplied to an engine is not all
available for pulling the cars; a large portion of the fuel is lost in
smoke, and another portion is wasted as ashes. So it is with the fuel
that runs the body. The food we eat is not all available for
nourishment, much of it being as useless to us as are smoke and ashes
to an engine. The best foods are those which do the most for us with
the least possible waste.

56. Fuel Value. By fuel value is meant the capacity foods have for
yielding heat to the body. The fuel value of the foods we eat daily is
so important a factor in life that physicians, dietitians, nurses,
and those having the care of institutional cooking acquaint themselves
with the relative fuel values of practically all of the important food
substances. The life or death of a patient may be determined by the
patient's diet, and the working and earning capacity of a father
depends largely upon his prosaic three meals. An ounce of fat, whether
it is the fat of meat or the fat of olive oil or the fat of any other
food, produces in the body two and a quarter times as much heat as an
ounce of starch. Of the vegetables, beans provide the greatest
nourishment at the least cost, and to a large extent may be
substituted for meat. It is not uncommon to find an outdoor laborer