10.1.3 Energy values of the different food types

Energy Values of the different food types:

• 1g carbohydrate= 4k/cals energy
• 1g protein= 4k/cals energy
• 1g fat= 9k/cals energy

Food Energy

The general term for all the chemical processes carried out by the cells of the body is "metabolism". Chief among these processes is the oxidation/burning of food which produces energy. This process is analogous to a car engine burning petrol to produce the energy that makes it run. In most forms of combustion, be it in the car or in the human, heat is produced as well as energy.

Classical physics taught that energy can be neither created nor destroyed. Although this law of nature is not completely correct (as the conversion of matter to energy in a nuclear reactor shows), it is still true in most instances. All three macronutrients in food - carbohydrate, protein and fat provide energy. Energy for the body comes mainly from food, and in the absence of food it can be produced only by the breakdown of body tissues.

All forms of energy can be converted into heat energy. It is possible to measure the heat produced by burning a litre of petrol, for example. Food energy can also be and is expressed as heat energy. The unit of measurement used has been the large calorie (Cal) or kilocalorie (kcal) (which is 1 000 times the small calorie used in physics).

Diet & Nutrition : What Is the Energy Value of Food?

Uploaded by eHow on Dec 16, 2008