What is adipose tissue?

Adipose tissue is a type of connective tissue that plays an important role in the functioning of the body. Better known simply as "fat," adipose tissue makes up about 15-20% of the average person's body weight. While many people have negative associations with deposits of adipose tissue in the body, people cannot thrive without it, although unusually high levels of this type of tissue have been linked to 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 stored lipids for the body. Both types include adipocytes, cells that are designed for fat storage, 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, white and brown cells also have slightly different physical structures.

One of the main functions of fat in the body is to provide stored energy reserves that are used to fuel the body between meals and during fasting periods. Brown adipose tissue also generates heat, which keeps the body at a stable temperature. In people with insufficient amounts of adipose tissues, it can be difficult to keep the body functioning between meals, and reduced body temperatures are common as the body cannot maintain a stable temperature.

The deposits immediately below the skin also help insulate the body, because adipocytes do not conduct heat as easily as other types of cells. This trait is used by many marine mammals to build a layer of fat that keeps the animal warm in cold water. Fat also acts as a shock absorber to protect the body from harsh impacts, and organs are wrapped in layers of visceral fat that do the same thing.

Adipose tissue is also related to the production of certain hormones. Deposits of this tissue form in different ways in different bodies, with women prone to depositing on the buttocks, thighs, and breasts, while men tend to collect 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 over the course of pregnancy to build reserves for the fetus and for lactation.

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