12 Enlightening Facts About Body Fat

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The human body is an amazing thing. For each one of us, it’s the most intimate object we know. And yet most of us don’t know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

Let’s face it: Fat gets a bad rap. 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 is a major site of energy storage, and has a key role in the regulation of metabolism and insulin production in your body—not to mention, it helps keep you warm. Having too much fat can be a bad thing, but having too little can pose problems as well.

Fat is stored in the body in the form of triglycerides, free fatty acid (FFA) molecules that are held together by a molecule called 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 your blood stream. (These are the ones most easily broken down through exercise.)

Before you demonize fat, take a look at these 12 facts about your adipose tissue.

1. FAT IS AN ORGAN …

Your 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,” Indraneil Mukherjee, a doctor at The Southeastern Center for Digestive Disorders and Pancreatic Cancer, Florida, tells Mental Floss. 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.

2. … AND IT PLAYS A KEY ROLE IN YOUR METABOLISM.

Adipose tissue is “a metabolically dynamic organ,” according to a study in Archives of Medical Science, whose primary job is to store excess energy. 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 disease: most obviously, obesity.

3. 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.

4. BROWN FAT KEEPS YOU WARM—AND IS NEWLY DISCOVERED IN ADULTS.

Brown adipose tissue is typically found in newborn human babies 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.

Up until recently, researchers weren’t sure brown fat existed in adults. “There's a lot of excitement around the discovery,” Yi Sherry Zhang, an assistant professor at the TOPS Obesity and Metabolic Research Center at the Medical College of Wisconsin, tells Mental Floss. “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.”

5. TOO MUCH OR TOO LITTLE FAT CAN INCREASE YOUR RISK OF DIABETES.

While it is now commonly known that obesity—when a person carries more weight than is considered healthy for their height—can predispose a person to type 2 diabetes, too little fat has a similar effect, according to the American Diabetes Association. Type 2 diabetes is a group of diseases in which the body has an impaired ability to produce or respond to the hormone insulin. And it turns out 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.

6. YOUR LEVEL OF BODY FAT MAY BE INFLUENCED BY YOUR MICROBIOME.

Researchers at McMaster University have begun studying a new realm of therapies known as postbiotics, the by-products that bacteria leave behind, which help the body synthesize insulin more effectively. In a new study, scientists discovered that administering postbiotics to mice with obesity reduced their insulin sensitivity—without any need for weight loss—heralding promising potential treatments for obesity with type 2 diabetes.

7. EXCESS FAT IS THE PERFECT ENVIRONMENT FOR CANCER.

Adipose tissue also secrets “hormones that make cancer cells grow quicker,” says Mukherjee. In fact, when adipose tissue expands, it also allows more immune cells to enter the tissue. These B and T immune cells secrete pro-inflammatory molecules such as adipokines [PDF]—peptides that signal other organs—and cytokines, which create the perfect microenvironment for tumor growth, according to a study in Frontiers in Physiology.

8. YOU CAN MOVE YOUR FAT AROUND.

If you are so inclined, Mukherjee points out that “fat transplant is legal”—so you can technically surgically move it from one body part to another without any harm done, “for vanity,” he says. These so-called fat transfers can augment a formerly flat part of your body, but buyer beware—not only can you experience the side effects of surgery such as swelling, bruising, several weeks of recovery time, you can develop lumps.

9. DIETING DOESN’T REDUCE THE NUMBER OF FAT CELLS YOU HAVE.

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 says. Zhang adds, “Each of us has 10 billion to 30 billion fat cells in our body.” Obese people can eventually have up to 100 billion fat cells.

10. YOUR FAT COMMUNICATES WITH OTHER ORGANS ALL OVER THE BODY.

It does so by sending out small molecules called microRNAs (miRNAs) that control gene activity, according to a study in Nature. After injecting genetically modified mice with fluorescent liver cell miRnas, 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.

11. THE GENETIC UNDERPINNINGS OF FAT MAY HELP TREAT OBESITY.

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

12. IN FACT, EPIGENETICS IS THE NEW FRONTIER OF FAT RESEARCH.

Researchers studying fat to better understand metabolic disorders recently focused on the field of epigenetics, which is the study of “the various elements that regulate which genes are active in particular cells and how they are regulated,” Zhang says. She 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.”

8 Surprising Facts About Your Nose

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iStock/AntonioGuillem

Your nose is more than just a bump on your face—it’s an important part of the respiratory system and affects many other senses, including your taste and hearing. For being something that’s so central to our daily interactions with the world, there’s still a surprising amount to discover about the nose. Here's a bit of what we do know.

1. Your nose can detect billions of different odors.

Although the human nose is weak compared to canine sniffers, our noses can detect 1 trillion smells. Strangely, scientists still aren’t sure exactly how we smell. For decades, researchers thought the olfactory system worked through receptor binding, meaning molecules of different shapes and sizes bonded to specific parts of the nose like puzzle pieces, triggering smell recognition in the brain. But recently, biophysicist Luca Turin has proposed the nose detects smell through quantum vibrations. Turin suggests the frequency at which different molecules vibrate helps the nose identify them as different scents. The theory could explain why molecules of the same shape smell quite differently. Intriguing as it is, this new theory hasn’t been tested enough to be universally accepted.

2. Our big brains might have caused our noses to protrude.

As anyone who’s been to a zoo probably knows, great apes (the closest human ancestors) have flat nasal openings—and researchers found that type of nose is far more effective at inhaling air than the human version. So what’s up with ours? Scientists think the shape might be a by-product of our big brain. The growing cerebellum forced human faces to become smaller, which probably affected the nose as well.

3. Women's noses are more sensitive than men's.

In the battle of the sexes, women’s noses come out on top. When tested for odor detection and identification, women score consistently higher than men. This might have something to do with the size of their olfactory bulb, a structure in the brain that helps humans identify smells. One study found that women have, on average, 43 percent more cells in their olfactory bulb than men do—meaning they can smell more smells.

4. Holding your nose really does help you swallow something distasteful.

Think you like chocolate just because it tastes good? Think again. Smell is responsible for 75 to 95 percent of flavor, which explains why plugging your nose helps you swallow something unappetizing. More recently, chefs and neurologists have teamed up to create meals for cancer patients and others with a diminished sense of smell, such as the elderly. Cooking meals tailored to the smell-less could help stave off depression and improve the appetite without relying on sugar and salt.

5. Surgeons can regrow damaged noses.

When people have cancer or are in an accident, the nose can become infected or even be completely destroyed. But fear not. Plastic surgeons have a way to regrow your nose—on your forehead. Using cartilage from the ribs and tissue expanders that allow the skin to stretch and grow, a new nose can be formed to replace the old one. And while a nose growing out of your forehead looks odd, it's actually one of the best places for a new nose to grow. The forehead's blood vessels can be harnessed to help grow the tissue, and removing the new nose only leaves a small scar [PDF]. Doctors have performed the procedure in the U.S., China, and India.

6. Your nose can sense more than smells.

The nose doesn’t just translate odors in the nasal passage—the tip is also full of nerves that detect pain and temperature. This helps us “smell” non-odor smells. Even people who can no longer smell things with their olfactory system can detect substances like menthol, the minty compound that makes your skin tingle. (Unfortunately, they can’t detect pure scents like vanilla.)

7. About 20,000 liters of air pass through the nose every day.

The average adult breathes around 20,000 liters of air every day, which keeps the nose quite busy. As the first line of defense for the lungs, the nose filters out small particles like pollen and dust. It also adds moisture to the air and warms it so the lungs are saved from any irritation.

8. Anosmia is just one of several smell disorders affecting the nose.

There are plenty of things that can go wrong in your nose. Allergic rhinitis, sinus infections, and broken noses are just a few. But perhaps less well known are disorders that affect the nose’s ability to smell. Anosmia is the complete inability to detect odors and can be caused by illness, aging, radiation, chemical exposure, or even genetics. Equally bizarre are parosmia and phantosmia: The former changes your perception of smells, and the latter creates the perception of smells that don’t exist. Luckily, only 1 or 2 percent of North Americans suffer from any smell disorders.

Why Do We Get Shivers Up Our Spines?

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iStock.com/martin-dm

Picture this: You're sitting on your couch in the dark alone, watching a scary movie. The killer is walking toward an unsuspecting victim, then suddenly jumps out at her. In that moment, the hairs on your body stand up, and you get a shiver down your spine. When you go for a walk on a crisp morning, the same thing happens. When the music swells during your favorite song, you get the shivers again, this time with the little goosebumps on your arms that appear when you get that sensation.

There's a good reason for shivers and goosebumps: they're your body's response to emotion or stress. We got this from our animal ancestors. When they were cold, the hair on their bodies would stand up—the movement of the arrector pili muscle would cause the skin to contract, raising each hair—to provide an extra layer of insulation. This response is also in play when animals feel threatened: their natural reaction is to try to look bigger than their attacker, so their skin and hair expand to play up that effect. The part of the brain called the hypothalamus is what controls this reaction.

So why do goosebumps—also known as cutis anserina or piloerection—appear, aside from the functional purpose of looking larger or creating insulation? It's because our emotions are also connected with the hypothalamus, so sometimes goosebumps are just our body reacting to our brain's signals of intense emotion.

When we feel things like love, fear, or sadness, the hypothalamus sends a signal to our bodies that produces adrenaline in our blood. The signal triggers the arrector pili muscles to contract, and then we have goosebumps caused by emotion. The sudden adrenaline rush may also cause sweaty palms, tears, increased blood pressure, or shivers.

When we listen to music and get shivers, it is a mixture of subjective emotions toward the music and physiological arousal. If we hear a song we get excited about, or a song that makes us sad, the hypothalamus reacts to the sudden change in emotion and we physically feel the shiver along our spine.

This article was republished in 2019.

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