Mechanical cushion (adipose tissue also surrounds internal organs and provides protection for these organs.)

The excess calories (consumed more than what actually needed for the current physical activity ) is stored in adipose tissue. Carbohydrate and protein consumed in the diet can be converted to fat. The carbohydrates can be stored as glycogen in the liver and muscle and can also be converted to triglycerides in the liver and transferred to adipose tissue for storage. Amino acids from proteins are used for new protein synthesis or they can be converted to carbohydrate and fat.
Fatty acids, in the form of triglycerides are consumed through the diet or synthesized by the liver .Very little synthesis of free fatty acids occurs in the cells of adipose tissue (adipocytes). Triglycerides are the most important source of fatty acids, because this is the form in which dietary lipids are assembled by the digestive system and liver.
Triglycerides are made up of long chain of fatty acids .These are hydrolyzed (broken) to glycerol and free fatty acids by an enzyme called Lipoprotein Lipase (LPL). The free fatty acids are taken up by cells of adipose tissues and stored again as triglycerides through a complex process

Insulin stimulates LPL formation. The LPL breaks the circulating to free fatty acids which can enter the adipocyte. Insulin is also required for the transport of glucose, which is needed for conversion of free fatty acids to tryglycerides in adipocytes. The conversion of glucose to fatty acids is accomplished by insulin's activation of several enzymes.