The basis of the science of dietetics is, like the basis of all sciences, a standard of measurement. The reason poetry is not a science is that while you can say “Keats”Ode on a Grecian Urn’ is beautiful” you cannot answer the question “Exactly how beautiful is it?”
Physics is a science because you can say not only “It will take a lot of work to pull that wagon up that hill” but also “Now, having weighed the wagon and measured the hill, I know it will take exactly so many foot-pounds to do that work.”
And all the sciences, from mathematics to psychology, are scientific or not just to the extent that you can measure exactly the operations they describe.
On this basis, dietetics is pretty high in the scale of the sciences.
Its fundamental basis of measurement is the calorie. Dietitians apply the term “calorie” to food values, but it really is a measurement of heat in all physical science. It also, of course, can be converted into a mechanical term of energy.
By strict definition a calorie is the amount of heat which will raise one kilogram of water one degree centigrade. Most of us do not think in terms of kilograms and degrees centigrade, no matter how hard they have been trying to get us to adopt the metric system, so it may be more graphic to say that a calorie is the amount of heat which will raise one pound of water four degrees Fahrenheit.
But to illustrate exactly what a calorie is we shall have to be more graphic. Other things besides food in burning release calories. A pound of wood will release about 2,500 calories. A pound of coal about 4,000.
Measurement of a calorie is done by using an apparatus which explodes a bomb inside a metal cask surrounded by water. The ex-plosion of the bomb heats up the water and this rise in temperature can be measured.
In mechanical terms, a calorie is the amount of energy which will raise a ton one and a half feet.