White adipose tissue can be subdivided into categories. The distinction between the two categories of white fat is made mainly by their location. The first type is the subcutaneous fat. Subcutaneous fat exists just below the surface of the skin and is the fat that is highly visible to the exterior because it sits between the muscle and skin. This means that subcutaneous fat is responsible for the loss of muscle definition that occurs in parts of the body such as the abdomen and the arms and legs. Generally, men tend to store white adipose tissue around their abdomen and waist, whereas women tend to store their subcutaneous adipose tissue around their hips and thighs. The difference between the male and female propensity to store white subcutaneous skin in different locations likely relates to the different sex hormone profiles between the sexes. The main functions of subcutaneous fat are to provide a store of energy as well as to provide a layer of insulation against the cold.
A second type of white fat exists that is often called abdominal fat or visceral fat. This fat is located around the internal organs on the abdomen and as its name suggests is located in the abdominal cavity deep to the surface of the skin. The main functions of this fat are to provide a cushioning effect on the vital organs as well as to supply a labile source of energy for the energy demands of the body. It is this source of fat that increases significantly with the development of insulin resistance, and the presence of large amounts of visceral fat increase the risk of cardiovascular disease significantly. Subcutaneous fat tends to be more stubborn when fat loss is being attempted and this relates to the nature of the visceral fat as a more labile store of energy. In particular, the subcutaneous fat around the abdomen in men and the thighs and hip is women is particularly stubborn, and even those who are considered quite lean still hold a large amount of white fat under the skin in these areas.
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