What are the two types of fat in human body?

• Overview

Overview

What is adipose tissue?

Adipose tissue, otherwise known as body fat, is a connective tissue that extends throughout your body. It’s found under your skin (subcutaneous fat), between your internal organs (visceral fat) and even in the inner cavities of bones (bone marrow adipose tissue).

Body fat is primarily known for storing and releasing energy and providing insulation. However, scientists now recognize that it’s also an active organ in your endocrine system. Adipose tissue contains nerve cells and blood vessels and communicates through hormone signals with other organs throughout your body. It has several important functions in regulating whole-body health. But these can malfunction if you have too much or too little of it.

Function

What is the function of adipose tissue?

Body fat serves many important functions, including:

• Energy storage and release.
• Insulation from cold and heat.
• Cushioning around soft organs.
• Regulating hunger and satiety.
• Maintaining energy balance.
• Regulating glucose and cholesterol.
• Maintaining insulin sensitivity.
• Generating thermogenic heat.
• Contributing to immunity.
• Metabolizing sex hormones.

How does adipose tissue collaborate with other organs?

By secreting some hormones and responding to others, adipose tissue communicates with other organs throughout your body, as well as with your central nervous system. It regulates energy supply and demand through hunger and satiety (feeling full) signals. It responds to insulin by converting excess blood sugar to lipids and storing them away for future use. Sex hormones partly determine where fat is deposited in your body. Adipose tissue also has its own active immune cells, which respond to certain stimuli by clearing out dead fat cells or producing an inflammatory response. Metabolic diseases result from a breakdown in these functions.

Anatomy

Where is adipose tissue located?

Adipose tissue is found throughout your body. The primary depots are:

• Subcutaneous adipose tissue (SAT). This is the fat that lives between your skin and muscles.
• Visceral adipose tissue (VAT). This is the fat that surrounds the organs in your abdominal cavity.

Other locations include:

• In bone marrow.
• In breast tissue.
• Between muscles.
• Around your heart.
• In your eye sockets.
• In the palms of your hands and soles of your feet.

A particular kind of adipose tissue, the brown kind, is mostly present in infancy and diminishes with age. It’s found in your upper back, above your clavicles and around vertebrae.

What does adipose tissue look like?

Adipose tissue can be classified as either white (WAT) or brown (BAT).

White adipose tissue

White adipose tissue is the most abundant type, appearing throughout your body as subcutaneous fat, visceral fat and bone marrow fat. White fat cells (adipocytes) have a simple structure composed of a single lipid droplet (fat molecule) and a few cellular organelles. They provide energy storage, insulation from extreme temperatures and cushioning around soft organs. WAT also includes other cell types, called stromal vascular fraction (SVF) cells. Together, these cells secrete hormones that help regulate energy balance, hunger and satiety, metabolism and inflammatory response.

Brown adipose tissue

Brown adipose tissue in humans is mostly present in infancy and diminishes with age. It’s located primarily in your upper back. Brown adipocytes (fat cells) are more complex than white adipocytes, containing multiple lipid droplets and many cellular organelles. The iron content in these organelles gives brown fat cells their color. These organelles enable the brown adipocytes to generate a large amount of heat. This is the primary function of BAT — to generate heat through a process called non-shivering thermogenesis, which helps protect infants from hypothermia.

Conditions and Disorders

Is it healthy to have adipose tissue?

Adipose tissue is crucial for health. However, having too much — or too little — can cause its regulatory systems to malfunction. Healthy levels vary by age and sex, ranging between 10% and 35%. In the case of obesity, the body runs out of tissue to store lipids in, so the existing fat cells have to grow. Enlarged fat cells are associated with chronic inflammation and with a variety of metabolic disorders that follow. Ironically, a lack of overall fat tissue can cause the same effects because, again, the body doesn’t have enough existing tissue to store lipids in.

What are the common conditions and disorders that affect this body system?

Dysfunctional adipose tissue can lead to various metabolic disorders, including:

• Insulin resistance, resulting in diabetes.
• Dysfunctional hunger and satiety signals, resulting in obesity.
• Hypertension and heart problems.
• Fat storage in the organs and fatty liver disease.

How are adipose tissue disorders treated?

Besides genetic factors, most disorders of the adipose tissue result from malnutrition, which can mean either undernutrition or overnutrition. Undernutrition is treated with supplemental nutrition or “refeeding.” Overnutrition is treated first with diet and exercise. For more advanced obesity (class III), medication or surgery may be an option. Obesity is associated with various metabolic disorders, but not all people with extra body fat have metabolic issues. Specific complications, such as insulin resistance, may require direct treatment.

Care

How should I take care of my adipose tissue?

Adipose tissue functions best in healthy amounts. For guidelines on the amount you want to aim for, the body mass index (BMI) can be useful. The chart estimates your body fat based on your height and weight and indicates a healthy range. It’s just a generalized chart, though, and not perfectly accurate. A visit with your regular healthcare provider can give you more personalized information, taking into account your balance of fat to muscle and fluid levels. Your provider could also help you set realistic goals for weight loss or weight gain.

For general care, though, you don’t need to get caught up in numbers. Just try to eat a healthful, balanced diet and get some regular exercise. Healthcare providers recommend a minimum of 30 minutes of moderate exercise, five days a week. That could mean taking a brisk walk, going for a bike ride, swimming or mowing the lawn. If you engage in more vigorous exercise, such as running, aerobic dancing or heavy yard work, two or three times a week is enough.

A note from Cleveland Clinic

Body fat is so much more than storage. Adipose tissue interacts with your entire body to maintain your metabolic homeostasis. Through chemical signals and adaptive responses, adipose tissue could even be said to function with intelligence — at least in the sense that other body systems do. And like other body systems, it can also function imperfectly, leading to a breakdown in various chemical processes that depend on it. The more we understand how interdependent all body systems are — including body fat — the more we understand how each one deserves our respect and care.

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Last reviewed by a Cleveland Clinic medical professional on 08/18/2022.

References

• Kershaw EE, Flier JS. Adipose tissue as an endocrine organ. (https://academic.oup.com/jcem/article/89/6/2548/2870285) J Clin Endocrinol Metab. 2004 Jun;89(6):2548-56. Accessed 8/18/2022.
• Osmosis. Adipose Tissue: What Is It, Location, Function, and More. (https://www.osmosis.org/answers/adipose-tissue) Accessed 8/18/2022.
• You and your Hormones. Adipose tissue. (https://www.yourhormones.info/glands/adipose-tissue/) Accessed 8/18/2022.

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