Fats come directly from the food we eat and are broken down in the digestive system by an enzyme called lipase before being transported in the blood stream. Both muscle and fat cells absorb the digested fats and either burn the fat through activity or store it for later use.
The fact is, however, that humans need fat as part of a healthy diet. Essential fatty acids must be obtained from food because the body has no way of producing them internally.
Fat for Energy
Certain vitamins (vitamins A, D, E, and K) are fat soluble, and eating fat is the only way to get these vitamins into the body.
Fat contains twice as many calories per gram as either proteins or carbohydrates, which makes fats an excellent source of energy. This is fine — as long as that energy is used.
Fat in the Body
Fat is found in several places throughout the body. The majority is stored just under the skin. The thickness of the fat under the skin varies from body area to body area. It tends to be thickest at the waist, and is practically nonexistent at the eyelids.
Fat is stored to be used when food is not being eaten and provides energy required for exercise.