Adipose tissue is a type of connective tissue which plays an important role in the functioning of the body. Better known simply as “fat,” this tissue makes up around 15-20% of the body weight of an average person. While many people have negative associations with deposits of adipose tissue on the body, people cannot thrive without it, although unusually high levels of this type of tissue have been linked with health problems.
There are two types of adipose tissue: white and brown. In addition to appearing in different colors, these types have slightly different functions, and different levels of lipids in storage for the body. Both types include adipocytes, cells which are designed for the storage of fat, and the cells can store different types of lipids in varying concentrations, with brown adipose tissue varying considerably in color and lipid composition. Under a microscope, the white and brown cells have slightly different physical structures as well.
One of the primary roles of fat in the body is to provide reserves of stored energy which are used to fuel the body between meals and during periods of fasting. Brown adipose tissue also generates heat, which keeps the body at a stable temperature. In people with insufficient quantities of adipose tissues, it can be difficult to keep the body functioning between meals, and lowered body temperatures are common as the body is unable to keep itself at a stable temperature.
Deposits found immediately below the skin also help to insulate the body, because adipocytes do not conduct heat as readily as other types of cells do. This trait is used by many marine mammals to build up a layer of blubber which keeps the animal warm in cold water. Fat also acts as a shock absorber to protect the body from heavy impacts, and the organs are wrapped in layers of visceral fat which serve the same function.
This type of tissue is also linked with the production of certain hormones. Deposits of this tissue form in different ways on different bodies, with women being prone to deposits on the buttocks, thighs, and breasts, while men tend to accumulate deposits around their stomachs. In women, the percentage of adipose tissue tends to be higher, to prepare the body for the heavy energy demands of pregnancy. Pregnant women also tend to develop additional deposits in the course of the pregnancy to build up reserves for the fetus and for breastfeeding.