Adipose tissue

Your body has fat.

It helps keep you warm. It also keeps you safe. It is like a soft cushion.

Fat stores energy for later. It also helps you feel full. This tells your brain when to eat.

There are two kinds of fat. White fat stores energy. Brown fat makes heat to keep you warm.

You can find fat in many places. It is under your skin. It is also around your organs.

Some fat is deep inside your belly. This is called visceral fat. It is different from the fat under your skin.

Your body has a special kind of tissue called adipose tissue. Most people just call it fat.

This tissue does many jobs. Its main job is to store energy. It does this by holding onto lipids, which are fats. This energy helps your body when you need it. Adipose tissue also acts like a cushion for your organs. It can even act like a blanket to keep you warm.

There are two main types of fat. White adipose tissue stores energy for the body. Brown adipose tissue is different. It makes heat to keep you warm.

You can find fat in many spots. Some is just under your skin. This is called subcutaneous fat. Other fat is deep inside your belly. This is called visceral fat.

Visceral fat sits between your organs, like your stomach and liver. Having too much visceral fat can lead to health problems. This includes things like type 2 diabetes. Scientists also found that fat is an endocrine organ. This means it makes hormones. These are tiny signals that tell your body how to work.

Your body has a special kind of tissue called adipose tissue. Most people simply call it fat.

This tissue is made of many different parts. Most of it is made of cells called adipocytes. It also holds other cells like immune cells and blood vessel cells. This group of extra cells is called the stromal vascular fraction. Adipose tissue is very important for staying healthy. It acts as a reserve of energy for your body.

Adipose tissue works in a very clever way to manage energy. It stores energy in the form of lipids, which are fats. When your body needs energy, these lipids can be used up. The tissue also helps manage sugar in your blood. It stores triglycerides, which are fats made by your liver from sugars. This process helps protect your body from having too much glucose. The movement of these fats in and out is controlled by signals. These signals include things called insulin and leptin.

Scientists have learned a lot about fat over a long time. A Swiss naturalist named Conrad Gessner first identified brown adipose tissue in 1551. For a long time, people thought fat was just a quiet storage spot. They thought it was hormonally inert, which means it did not send signals. Now, we know it is actually a major endocrine organ. An endocrine organ is a part of the body that makes hormones. These hormones, like leptin and estrogen, tell your body how to act.

There are two main types of this tissue in your body. White adipose tissue is used to store energy. Brown adipose tissue is different because it generates body heat. You can find these tissues in many specific places called depots. In humans, some fat is just under the skin. This is called subcutaneous fat, and it helps keep you warm. Other fat is deep inside your belly around your organs. This is called visceral fat.

Understanding where fat sits helps us understand health. Subcutaneous fat is often found in the hips and thighs. Having this kind of fat is generally considered a lower health risk. However, having too much visceral fat can be a hard job for the body. Too much visceral fat is linked to things like type 2 diabetes. It can also be linked to heart disease. Doctors can use tools like the Body Volume Index to measure this fat. Staying active with exercise can help reduce visceral fat levels.

Adipose tissue, commonly known as body fat, is a specialized type of loose connective tissue. It is primarily composed of cells called adipocytes, which act as storage units for energy.

However, the tissue is more complex than just fat cells. It contains a group of various cells called the stromal vascular fraction (SVF). This fraction includes preadipocytes, which are cells that can become fat cells, and fibroblasts. It also contains vascular endothelial cells that form blood vessels, and immune cells like adipose tissue macrophages. While it was once thought to be hormonally inert, meaning it did not send signals, scientists now recognize it as a major endocrine organ. This means it produces essential hormones like leptin, estrogen, resistin, and cytokines.

The way adipose tissue manages energy is a continuous, regulated process. The tissue stores energy in the form of lipids, which are fats. To manage these fats, the body uses a process involving free fatty acids (FFAs). These FFAs are released from lipoproteins by an enzyme called lipoprotein lipase (LPL). Once inside the adipocyte, the FFAs are reassembled into triglycerides. This reassembly happens by attaching the FFAs to glycerol through a process called esterification.

The movement of these fats in and out of the tissue is a constant flux. This flux is controlled by the hormones insulin and leptin. When insulin levels are elevated, there is a net inward movement of FFAs into the cells. The FFAs can only leave the adipose tissue when insulin levels are low.

There are two distinct functional types of adipose tissue: white and brown. White adipose tissue (WAT) is the primary site for storing energy. It also helps protect the body from excess glucose by storing triglycerides produced by the liver. Brown adipose tissue (BAT) serves a different purpose by generating body heat.

These tissues are located in specific areas known as adipose depots. In humans, these depots include subcutaneous fat, which sits just beneath the skin in the hypodermis. It provides insulation against heat and cold. Another major type is visceral fat, which is located deep inside the abdominal cavity. This fat is packed between internal organs like the stomach, liver, and intestines.

History shows that our understanding of these tissues has evolved significantly. The Swiss naturalist Conrad Gessner first identified brown adipose tissue in 1551. For centuries, the scientific view was that fat was simply a passive storage depot. Modern research has changed this by revealing the active role of adipose tissue in the endocrine system. We now understand how it communicates with the brain to provide feedback regarding hunger and diet. For example, in mice, a lack of the hormone leptin can cause a mouse to feel constant hunger. This leads to excessive eating and eventually obesity.

The location of fat depots has major implications for human health. Subcutaneous fat, often found in the hips, thighs, and buttocks, is generally considered to pose a lower health risk. In contrast, an excess of visceral fat is linked to serious conditions. This includes type 2 diabetes, insulin resistance, and cardiovascular diseases like atherosclerosis.

Excess visceral fat is often called abdominal obesity or "belly fat." Men are often more likely to store fat in the abdomen due to sex hormone differences. For instance, estrogen helps women store fat in the hips and thighs. When estrogen levels decline during menopause, fat often migrates toward the waist.

Scientists use various methods to study and measure these fat stores. To estimate body density, researchers have used equations from Durnin and Wormersley based on skinfold measurements. While these are only estimates, they help model the relationship between subcutaneous fat and total body fat. For abdominal fat, new developments like the Body Volume Index (BVI) help measure abdominal volume specifically.

Another important area of study is marrow adipose tissue (MAT). This is a poorly understood depot located within the bone. It is interspersed with bone and hematopoietic cells. Interestingly, MAT increases during calorie restriction, which is different from how other fat depots behave.

Finally, it is important to distinguish between healthy fat storage and ectopic fat. Ectopic fat occurs when triglycerides are stored in tissues that are not meant to hold them. This includes the liver, skeletal muscle, heart, and pancreas. This accumulation can interfere with how these organs function and is associated with insulin resistance. While visceral fat is a specific depot in the abdomen, ectopic fat is the misplaced storage of fat within other organs. Managing total body fat through diet and exercise can help reduce both visceral and ectopic fat stores, improving overall organ function.