Fats are the most concentrated source of energy
Fats are solid at room temperature (20 degrees
celcius). They are called oils if they are liquid at 20 degrees
Animal fats: Butter, milk, cheese, eggs, fat of
meat and fish, ghee
Vegetable fats: Oils of plant seeds like groundnut,
mustard, sesame, cocount etc. (properly called vegetable oils rather
than vegetable fats).
Other sources: small quantities of fat are found
in most other foods such as cereals, pulses, nuts and vegetables.
Rice and wheat have 3% fat in them, each. Hence, large cereal consumption
provides considerable amounts of invisible fat.
Even if a diet is deficient in fat, our body has
got the special ability to convert excess carbohydrate into fat
for storage purposes.
Provide energy (9 Calories per gram)
By providing energy, fats spare proteins from being
used up for energy. This is called protein-sparing effect of fat.
Fats serve as vehicles for fat soluble vitamins
(vitamins A, D, E, and K).
Fat beneath the skin keeps us warm in cold weather.
Fat deposited around internal body organs protects
them like a cushion.
Fat imparts better taste to food. Remember the
difference in taste between a boiled potato and fried potato?
Vegetable oils are rich sources of Essential Fatty
Acids (see below).
Fats (visible + invisible fats) should provide
no more than 30% of total calories in the diet. If you need 2400
calories in a day, for example, then fat in your diet should provide
not more than 800 calories in it.
At least half of this total fat intake should consist
of vegetable oils. They are rich in Essential Fatty Acids with numerous
positive effects to health.
The lower the fat intake, the lesser the risk
of coronary heart disease.
Visible and invisible fats
Visible fats are those that have been separated
(and hence concentrated) from their natural sources. For example,
butter is obtained from milk. Such fat can easily be quantitated
and hence its caloric value is easy to calculate.
On the other hand, the invisible fats are those
that are present in their natural sources (for example, we talked
about 4% fat in wheat and rice). Such invisible fat is present in
almost every food. Their contribution to diet cannot be calculated
The major contribution to diet comes from invisible
fats. Visible fats are of a limited value.
It is a process in which hydrogen is added to the
vegetable oils under optimum temperature and pressure in the presence
of a catalyst. The process renders liquid oils into semisolid or
solid fats. The main advantage of hydrogenation is that the fat
is able to maintain its quality in hot and humid climates. Such
hydrogenated fat is a very popular cooking medium in India.
The disadvantage of hydrogenation is that the unsaturated
fatty acids are converted into saturated acids and the Essential
Fatty Acid content is drastically reduced. The vitamin content undergoes
a reduction too. It is therefore advisable (and mandatory in many
countries) to fortify such hydrogenated fat with Vitamins A and
Refining of oils is usually done by treatment with
steam, alkali etc. This process removes the free fatty acids and
other rancid materials, thereby improving the palatability (taste).
Refining does not bring about any change in the
Unsaturatty fatty acid content of the oil. It only improves the
quality and taste of oils. Quite understandably, refined oils are
costlier than their natural counterparts.
Diseases caused by Fat
Obesity: A diet rich in fat can encourage obesity
and thus endanger the health. Obesity poses multiple threats to
the health, and can be measured easily by Body Mass Index (BMI).
Phrenoderma: Deficiency of essential fatty acids
in the diet leads to a rough and dry skin, a condition called phrenoderma
(Toad Skin). Phrenoderma is characterised by rough rash like eruptions
on the back and sides of arms and legs, the back, and the buttocks.
It can be cured by giving linseed of safflower oil which are rich
in Essential Fatty Acids.
Coronary Heart Disease: High fat intake (particularly
the saturated fat), is one of the major risk factors leading to
coronary heart disease. LDL (Low density lipoprotein) and VLDL (Very
low density lipoprotein) are harmful, while HDL (High density lipoprotein)
protects against Coronary heart disease. The higher the intake of
essential fatty acids in diet, the lower the risk of developing
(and dying from) Coronary heart disease.
Cancer: High dietary fat intake can increase the
chances of developing breast and colon cancers.