The body’s fat, also known as adipose tissue, plays many important functions beyond just supporting body shape, including storing energy, regulating temperature, and producing hormones.
Subcutaneous fat is visible underneath the skin and can be physically pinched, whereas visceral fat is found around our organs.
In addition to an MRI or CT scan, waist circumference can also be used to measure visceral fat (Please note: if you are recovering from disordered eating, we do not recommend measuring your waist circumference).
There are two types of fat cells in adipose tissue: white and brown. Adults store energy in white fat, which makes up the majority of their fat.
In contrast, brown fat is used for expending energy and producing heat. Brown fat is believed to help newborns regulate their body temperature, and its amount decreases as they grow older.
The Functions of Body Fat
1. Energy stores
Lipids perform many tasks in the body, but most importantly they provide energy. A constant flow of energy is so vital to life that, in a pinch, any other function is sacrificed to maintain it. The stores of glycogen in the liver provide glucose to the blood whenever the supply runs short. The body’s stores of glycogen are limited, however.
In contrast, the body’s capacity to store fat for energy is virtually unlimited due to the fat-storing cells of the adipose tissue. The fat cells of the adipose tissue readily take up and store fat, growing in size as they do so. Fat cells are more than just storage depots, however; fat cells secrete hormones that help to regulate the appetite and influence other body functions.
2. Muscle fuel
The fat stored in fat cells supplies 60 percent of the body’s ongoing energy needs during rest. The fat embedded in muscle tissue shares with muscle glycogen the task of providing energy when the muscles are active. During some types of physical activity or prolonged periods of food deprivation, fat stores may make an even greater energy contribution. The brain and nerves, however, need their energy as glucose.
3. Raw materials
Fats are converted to other compounds, such as hormones, bile, and vitamin D, as needed. Fat is an inefficient source of glucose. After a long period of glucose deprivation (during fasting or starvation), brain and nerve cells develop the ability to derive about half of their energy from a special form of fat known as ketones, but they still require glucose as well. This means that people wanting to lose weight need to eat a certain minimum amount of carbohydrates to meet their energy needs, even when they are limiting their food intake.
Fats insulate against temperature extremes by forming a fat layer under the skin. Natural oils in the skin provide a radiant complexion; on the scalp, they help nourish the hair and make it glossy. The layer of fat beneath the skin insulates the body from extremes of temperature.
A pad of hard fat beneath each kidney protects it from being jarred and damaged, even during a motorcycle ride on a bumpy road. The soft fat in a woman’s breasts protects her mammary glands from heat and cold and cushions them against shock.
6. Cell membranes
Fats form the major material of cell membranes. The phospholipids and the sterol cholesterol are cell membrane constituents that help maintain the structure and health of all cells.
Lipids in the body not only serve as energy reserves but also protect the body from temperature extremes, cushion the vital organs, and provide the major material of cell membranes.