Fats are also an important part of our diet. Many foods
contain fat in different amounts. High-fat foods include
dairy products like butter and cream as well as mayonnaise
and oils.
There are two kinds of fats: saturated and unsaturated.
Saturated fats are normally solid at room temperature,
while unsaturated fats are liquid at room temperature.
Vegetable oils are the best examples of unsaturated fats,
while lard and shortening (along with the animal fat you
see in raw meat) are saturated fats.
We can further distinguish the unsaturated fats between
polyunsaturated and monounsaturated. Unsaturated fats
are currently thought to be more healthy than saturated fats,
and monounsaturated fats (as found in olive oil and peanut oil)
are thought to be healthier than polyunsaturated fats.
Fat is necessary because: the only way to get certain
fat-soluble vitamins is to eat fat, your body has no way to
make certain essential fats, so you must get them in your
food.
Another reason is that fat is a good source of energy,
in fact it contains twice as many calories per gram as
do carbohydrates or proteins. Your body can burn fat as
fuel when necessary