Fats are hydrocarbons consisting of carbon, hydrogen and oxygen. Fats are solids at 20° C. If they are liquids, they are called oils.
Classification of fats
1. Simple lipids e.g. triglycerides.
2. Compound lipids e.g. phospholipids.
3. Derived lipids e.g. cholesterol.
On hydrolysis, fats yield fatty acids and glycerol. Fatty acids are classified as:
1. Saturated fatty acids e.g. lauric, stearic and palmitic acids.
2. Unsaturated fatty acids which may be monounsaturated (e.g. oleic acid) or polyunsaturated (e.g. linoleic acid).
Animal fats contain saturated fatty acids. Vegetable oils mostly contain polyunsaturated fatty acids.
Essential fatty acids
These are fatty acids which cannot be synthesised in the body. They are derived only from food. The essential fatty acids necessary for growth are linoleic acid, linolenic acid and arachidonic acid.
Functions of fats
They provide energy (9 K cals per gram).
Vehichles for fat soluble vitamins (A, D, E and K).
They provide support to viscera like heart, kidney and intestine.
Fat beneath the skin provides insulation against cold.
They are rich sources of essential fatty acids.
Sources of fats: Thp dietary sources of fats are classified as:
1. Animal sources: Animal sources of fats are meat, fish, eggs, milk, ghee and butter.
2. Vegetable sources: They are vegetable oils obtained from ground nut, sesame, coconut and mustard.
3. Other sources: Minute quantities of fat are found in other foods such as cereals, pulses, nuts and vegetables. This fat is called invisible fat.
Diseases related to fat intake
Excess of fat intake can lead to obesity, coronary heart disease and cancer of breast and colon. Diet dificient in essential fatty acids can produce dry and rough skin (phrenoderma) and also skin lesions of kwashiorkar.
Fat intake should not be more than 20 per cent of total energy intake.