White adipose tissue or white fat is one of the two types of adipose tissue

Adipose tissue

In histology, adipose tissue or body fat or fat depot or just fat is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat; fat in its solitary state exists in the liver and muscles. Adipose tissue is derived from lipoblasts...

 found in mammals. The other kind of adipose tissue is brown adipose tissue

Brown adipose tissue

Brown adipose tissue or brown fat is one of two types of fat or adipose tissue found in mammals....

.

In humans, white adipose tissue composes as much as 20% of the body weight in men and 25% of the body weight in women. Its cells contain a single large fat droplet, which forces the nucleus to be squeezed into a thin rim at the periphery. They have receptors for insulin

Insulin

Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....

, growth hormones, norepinephrine

Norepinephrine

Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

 and glucocorticoids.

White adipose tissue is used as a store of energy. Upon release of insulin from the pancreas, white adipose cells' insulin receptors cause a dephosphorylation cascade that lead to the inactivation of hormone-sensitive lipase

Lipase

A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...

. Upon release of glucagon

Glucagon

Glucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is...

 from the pancreas

Pancreas

The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

, glucagon receptors cause a phosphorylation cascade that activates hormone-sensitive lipase, causing the breakdown of the stored fat to fatty acids, which are exported into the blood and bound to albumin

Albumin

Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...

, and glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, which is exported into the blood freely. Fatty acids are taken up by muscle and cardiac tissue as a fuel source, and glycerol is taken up by the liver for gluconeogenesis.

White adipose tissue also acts as a thermal insulator, helping to maintain body temperature.