Fats are composed of carbon, hydrogen and oxygen. They differ from carbohydrates that the percentage of these elements is different and there is less of oxygen in fats than in carbohydrates.
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There are many kinds of fats. Some fats such as groundnut oil and vegetable oil are liquid at room temperature and some fats such as ghee or butter are semisolid or solid in nature.
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Chemically fats are composed of glycerol and fatty acids. The latter may be saturated or unsaturated. In general animal fats contain saturated fatty acids and glycerin. It is found in eggs, meat, cheese, milk, butter and oily fishes. The vegetable fats contain the unsaturated fatty acids and glycerin. It is found in margarine and vegetable oils.
Fats are also called concentrated sources of heat and energy as 1 gm of fat yields 4 calories of heat on oxidation thus yield more than double the energy as compared to carbohydrates. Human body can synthesize triglycerides and cholesterol endogenously but those fatty acids which cannot be synthesized in the body are known as essential fatty acids which must be incorporated in the diet. Examples include linoleic acid and linolenic acid etc. which are mostly found in vegetable oils.
As fats are insoluble in water, during the process of digestion they are converted into an emulsion for their absorption into the body. Liquid fats and those which melt at body temperature are better digested than those which are much harder.
A fat rich diet slows the process of digestion and gives a feeling of heaviness and fullness. In the body, the fat which cannot be immediately used is partly deposited as adipose tissue under the skin and the rest unabsorbed is excreted along with the faces.
Sources of Fats:
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(a) Animal sources include ghee, butter, meat, fish oils etc.
(b) Vegetable sources include various vegetable oils such as groundnut oil, mustard oil, cottonseed oil, sunflower oil, coconut oil etc.
Functions of Fats:
The functions of fat are:
1. They are the concentrated source of energy and provide double the energy than that of carbohydrates and proteins. They provide energy especially in starvation.
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2. They act as carriers for fat soluble vitamins e.g. vitamins A, D, E & K.
3. They provide support to many organs of the body e.g. heart, kidneys eyes and intestines etc.
4. They supply essential fatty acids which are not found in the body.
5. Fat is used in the formation of cholesterol and steroidal hormones.
6. Fatty layer below the skin plays an important role in maintaining our body temperature thus protects the body from excessive heat and cold.
7. They increase the palatability of food and foods containing fats are tasty.