13 Enlightening Facts About Body Fat

Entire industries have been built upon the criticism and attempted reduction of body fat. But fat, formally known as adipose tissue, is a crucial part of your hormonal and metabolic processes. Adipose tissue stores energy and has a key role in the regulation of metabolism and insulin production—plus, it helps keep you warm. Having too much fat can be a bad thing, but having too little can pose problems as well. Take a look at these 13 facts about your adipose tissue.

1. Fat is stored in the body as triglycerides.
2. Fat is an organ.
3. Fat regulates your metabolism.
4. White fat gives you energy.
5. Brown fat keeps you warm.
6. Too much or too little body fat can increase the risk of diabetes.
7. Your microbiome might influence your amount of body fat.
8. Excess fat can increase your cancer risk.
9. Fat transplants are a thing.
10. Dieting does not reduce the number of fat cells in your body.
11. Body fat communicates with other organs.
12. Its genetic underpinnings may help treat obesity.
13. Epigenetics is the new frontier of fat research.

Fat is stored in the body as triglycerides.

Triglycerides are free fatty acid molecules that are held together by glycerol, a type of alcohol. Most of our body fat is stored in fat cells called adipocytes, but fat can also be stored as droplets within skeletal muscle cells. In addition, some triglycerides even roam freely in the blood stream. (These are the ones most easily broken down through exercise.)

Fat is an organ.

Fat is not just a layer of padding—it’s actually an organ of the endocrine system. “Fat secretes a lot of hormones while activating or deactivating many more,” Dr. Indraneil Mukherjee, a physician at the Northwell Health Florina Cancer Center in New York, told Mental Floss in 2017. It’s comprised of adipocytes and fat cell types called the stroma-vascular fraction, which are made up of growth factors—messengers the body uses to signal cells—as well as stem cells, blood cells, and a host of other cell types.

Fat regulates your metabolism.

Adipose tissue is “a metabolically dynamic organ” whose primary job is to store excess energy, according to a study in Archives of Medical Science. It also synthesizes “a number of biologically active compounds that regulate metabolic homeostasis.” In other words, it controls your body’s energy balance by regulating appetite signals from the central nervous system and metabolic activity in peripheral tissues. Chronic over-nutrition—eating too much on a regular basis—can cause inflammatory responses and metabolic disorders that can lead to obesity.

White fat gives you energy.

White adipose tissue stores your body’s reserves of energy, and the endocrine cells mentioned above, which secrete crucial hormones and molecules. There are even “adipose depots” where white adipose tissue tends to gather more easily, located around organs such as the heart, lung, and kidney.

Brown fat keeps you warm.

Brown adipose tissue is typically found in newborn humans and hibernating mammals, according to a study in Frontiers in Endocrinology. Its main function is to generate heat—keeping you warm—and to do so, it contains more mitochondria and capillaries than white adipose tissue.

Until recently, researchers weren’t sure brown fat existed in adults. “There's a lot of excitement around the discovery,” Dr. Yi Sherry Zhang, founder and chief science officer of the personalized nutrition company GenPalate, told Mental Floss in 2017. “It helps to regulate energy expenditure. This is important because drugs that target this type of fat may provide a new way to treat obesity.”

Too much or too little body fat can increase the risk of diabetes.

While it is now commonly known that obesity can predispose a person to type 2 diabetes, too little fat has a similar effect, according to the American Diabetes Association. Type 2 diabetes a condition in which the body doesn’t properly produce or respond to the hormone insulin. Having too little fat is due in part to a lack of a lipid-storing “compartments,” which leads to an imbalance of triglyceride and free fatty acid levels, leading to insulin resistance.

Your microbiome might influence your amount of body fat.

Researchers at McMaster University in Canada are studying postbiotics, the by-products that bacteria leave behind, which help the body synthesize insulin more effectively. Scientists have discovered that administering postbiotics to mice with obesity reduced their insulin sensitivity—without any need for weight loss—heralding potential therapies for people with obesity.

Excess fat can increase your cancer risk.

Adipose tissue also secrets “hormones that make cancer cells grow quicker,” Mukherjee said. When adipose tissue expands, it allows more B- and T-cells to enter the tissue. These immune cells secrete inflammatory molecules like adipokines, which send signals to other cells, and cytokines, which regulate the growth of blood cells and the body's immune response. The combo create the perfect microenvironment for cancer, according to a study in Frontiers in Physiology.

Fat transplants are a thing.

Mukherjee pointed out that “fat transplant is legal,” so you can surgically move fat from one body part to another for cosmetic pruposes without any harm done. These fat transfers can augment a formerly flat part of your body, but buyer beware: You may experience the side effects of surgery such as swelling, bruising, and several weeks of recovery time, or develop lumps in the transplanted tissue.

Dieting does not reduce the number of fat cells in your body.

The number of your fat cells can increase, but once the cellular structures have developed, they never go away. “With dieting, they just get smaller,” Mukherjee said. Zhang added, “Each of us has 10 billion to 30 billion fat cells in our body.” People with obesity may have up to 100 billion fat cells.

Body fat communicates with other organs.

Fat sends out small molecules called microRNAs that control gene activity, according to a study in Nature. After injecting genetically modified mice with fluorescent liver cell microRNAs, researchers saw a significant drop in liver cell fluorescence, which suggested that the fat tissue was communicating with the liver to regulate gene expression. They hope to further study this process to discover new treatment methods for obesity and type 2 diabetes.

Its genetic underpinnings may help treat obesity.

“We are beginning to understand the genetic basis for fat distribution and obesity,” Zhang said. “We have recently published genes that play a role in determining how body fat is distributed.” She hopes that these discoveries will help researchers understand the genetic component of common disorders like metabolic syndrome, type 2 diabetes, and obesity.

Epigenetics is the new frontier of fat research.

Researchers studying fat to better understand metabolic disorders have focused on epigenetics, the study of how various molecules activate or deactivate gene expression without altering DNA itself. Zhang believes that epigenetic changes are likely to play a critical role in the development of chronic disorders like metabolic syndrome and type 2 diabetes. “Unlike the genetic code, it is possible to reverse and alter these elements, which means we can potentially develop new ways to prevent and treat these common disorders,” she said.

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A version of this story was published in 2017; it has been updated for 2024.