The body is composed of a large number of cells which have a very active chemical life. To provide the with the material for all this, the food coming into the body has to be broken down and used up in many ways. All this activities requires oxygen and energy from food or fuel. The fuel, however, is not all the same; some fuels produce more heat that other–for example, fats will burn up more rapidly and produce more heat. Fats produce more heat for the same weight of food than any other food substance, and add to the food value of the diet quicker than other foods.
The needs for calories from food are affected by:
1. The kind of work a person does.
2. The age of the person, and his activity and state of growth.
3. Climate–more food is needed in a very cold climate.
4. Size–the need for food is in proportion to the body surface.
5. Pregnancy–food here is required for the growth of the foetus.
6. Breast-
feeding
Roughage
This is necessary to encourage peristalsis, and to provide bulk in the diet, and thus prevent constipation.
It is found in green vegetables, and fruit, and many of the bulky staple foods.
Water
This is necessary for the life of cells, the making of all secretions, al the chemical changes that take place in the body, helping enzymes to work, carrying out the waste products from the body, Regulating body temperature. Two-thirds of the body consists of water.
