what is the use of the fat in our body?

Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function.

Fats serve as energy stores for the body. Fats are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.

Fats also serves as a useful buffer towards a host of diseases. When a particular substance, whether chemical or biotic -- reaches unsafe levels in the bloodstream, the body can effectively dilute -- or at least maintain equilibrium of -- the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as the offending substances can be metabolized and/or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth.

Some fatty acids are essential nutrients, meaning that they can't be produced in the body from other compounds and need to be consumed in small amounts. All other fats required by the body are non-essential and can be produced in the body from other compounds.

Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats are sources of essential fatty acids, an important dietary requirement.

If you are also interested in the information of bad fats, see:
http://www.americanheart.org/presenter.jhtml?identifier=532

I have tried my best to help you.

2007-08-29 10:37:23 補充：
幫到你嗎?

Importance for living organisms
Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats are sources of essential fatty acids, an important dietary requirement.
Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. They also serve as energy stores for the body. Fats are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.
The fat content of a food can be analyzed by extraction. The exact method varies on what type of fat to be analyzed - for example, polyunsaturated and monounsaturated fats are tested quite differently.
Fat also serves as a useful buffer towards a host of diseases. When a particular substance, whether chemical or biotic -- reaches unsafe levels in the bloodstream, the body can effectively dilute -- or at least maintain equilibrium of -- the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as the offending substances can be metabolized and/or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth.
While it is nearly impossible to remove fat completely from the diet, it would be wrong to do so. Some fatty acids are essential nutrients, meaning that they can't be produced in the body from other compounds and need to be consumed in small amounts. All other fats required by the body are non-essential and can be produced in the body from other compounds.

fats have following function:
-serve as another energy source
-reduce heat loss
-help making cell membrane
-store surround the internal organ to act as a shock-absorber
-help to transport the fat-soluble vitamin