On Wed, 11 Aug 2004 16:45:56 -0400, "Andy Petro"
> wrote:

>Anyone know how the number of calories in the different kinds of food are
>measured . Is it chemical,heat or other .
>No one seems to be able to tell me.
>
Many science textbooks will go into this.

Calorie is a measure of heat energy that is possible from the chemical
energy stored in that material.

A heat calorie, usually with a small "c", is the energy required to
raise 1 gram of water 1 degree Centigrade at normal atmospheric
pressure.

A food calorie, usually with a large "C", is 1000 heat calories, also
a kcal.

Every chemical reaction will either absorb energy, called endothermic,
or release energy, called exothermic. Digestion of food releases the
stored energy in the food.

As a general rule, carbohydrates and proteins contain about 4 Calories
per gram, and fats and oils contain about 9 Calories per gram. Other
food ingredients do not contain usable calories, except for things
like alcohol (roughly 7 Calories per gram).

From this, you can look at the total grams of carbohydrates, fats, and
proteins in a serving of food, and calculate the total Calories for
that.

Further, your body digests the food, and converts it first to sugar in
the form of glucose or fructose (the simplest forms of sugar). Some of
this sugar is used right away by cells needing energy, some is stored
in the liver and muscles as glycogen, and the rest is stored as body
fat.

In other words, body fat does not come from specific types of food,
but from consuming more Calories than are used by your normal
metabolism plus exercise.

Also, burning food will release the same number of calories as one
could get from digesting it, and this is one traditional tool used to
assess the composition of a food or other material.

How did the energy get into the food in the first place? It is all
solar energy, stored in plants, or plant energy eaten by animals, and
stored in them.

HTH,
Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom