Fat and muscle are two words you often hear at the center of fitness and weight loss debates. In fact, whenever you hear the word fat, you probably have an adverse reaction. Whether you’re trying to lose weight or gain muscle, it’s important to avoid misconceptions about fat and muscle. While they are often intertwined, fat and muscle are actually two very different, unrelated substances in your body. To prove that fat and muscle are not frenemies, here are some common myths, debunked:

1. Myth or Truth

“Muscle weighs more than fat.”
MYTH. One pound of muscle weighs the same as one pound of fat, which weighs the same as one pound of feathers! A pound is a pound. Ten pounds are ten pounds, and no substance weighs more than another one. What many people don’t realize is that fat is bulkier than muscle tissue and takes up more space under the skin, explains author of Real Life Fitness, Jason Greenspan. The misconception here is a case of density and volume. One pound of fat is roughly the size of a small grapefruit, while one pound of muscle is about the size of a tangerine. That being said, muscle is active tissue, meaning that it burns more calories at rest than fat does.

2. Myth or Truth

“Muscle turns to fat when you stop exercising.”
MYTH. Fat and muscle are entirely different tissues, which means they are not interchangeable. When you’re working out and trying to build muscle, while losing weight, it’s easy to perceive that muscle turns to fat once you stop exercising. This is because muscles become less firm and decrease in size when they are not being used. Also, if you stop exercising, but don’t adjust how much food you are eating or what you are eating, you are likely to gain weight.

3. Myth or Truth

“You can turn fat into muscle by exercising.”
MYTH. Similarly to the point I made previously, the same goes for turning fat into muscle. Fat and muscle are completely different things. You can burn fat and build muscle simultaneously as you exercise…but they are not the same.

4. Myth or Truth

“All fat is the same—and bad!”
MYTH. Your body stores many different types of fat—and it’s not all bad! In fact, fat has more functions in your body than you might realize. As some of you already know, fat has two main purposes: to store excess calories in a safe way, so that you can mobilize the fat stores when you’re hungry and to release hormones that control your metabolism. The two well-known types of fat are white fat and brown fat. White fat is most commonly known, and responsible for, storing energy, as well as giving your body that little bit of extra insulation. Brown fat also stores energy, but when it burns, it creates heat without shivering (a process known as thermogenesis). During thermogenesis, brown fat also burns calories!

5. Myth or Truth


MYTH. As enticing as it sounds, there’s no such thing as an exclusively fat-burning heart rate zone. Even when you’re not exercising with intensity, your body is always working to turn carbohydrates and fat into energy your cells can use. This process is constant, but the primary source of energy changes, depending on what you’re doing, as well as other factors like your diet. As Paul Arciero, D.P.E., professor and director of the Human Nutrition and Metabolism Laboratory at Skidmore College explained to SELF in their article “The Myth of the Fat-Burning Zone,” if you eat a high-carb meal before exercising, your body will rely on those carbs first for energy, no matter the intensity of your workout.

6. Myth or Truth

“When you lose weight, fat disappears.”
TRUE, but kind of a MYTH, too. To this I would say…yes and no. When you lose weight, the amount of fat in your body decreases, but it doesn’t just turn into energy and disappear into the abyss or, as one of the top Google searches suggests, “come out in excretion.” In fact, a 2013 study performed by a team of Australian researchers found that you actually breathe out most of the mass that you lose during weight loss. We put on weight when excess carbohydrates and proteins are converted into triglycerides (compounds of carbon, hydrogen, and oxygen) and then stored inside fat cells. To lose weight, our bodies break down those triglycerides to access carbon. As the researcher’s results found, in order to completely breakdown 22 pounds of human fat, we need to inhale 64 pounds of oxygen (while burning calories). This reaction produces 62 pounds of carbon dioxide and 24 pounds of water.

We could probably go on forever when it comes to talking about fat and muscle, but this is enough to get the discussion started. Whether you’re looking to lose weight, build muscle, or just curious about what goes on in your body when you exercise, be sure to do your research and avoid misconceptions that might lead you to make unhealthy choices.