Fitness Lies It's Insane People Still Believe

Female lifting heavy weight
Jacob Lund/Shutterstock

In a world where everyone has a body, and therefore has an opinion on that body, the number of misconceptions surrounding physical fitness is astounding. Despite years of research refuting some of these long-held fitness myths, they continue to be passed around and passed down from gym generation to gym generation in a frighteningly inaccurate oral history of the human body. 

These are just a few of the glaringly obvious fitness lies it’s insane people still believe. 

Muscle weighs more than fat

A pound of muscle weighs a pound. A pound of fat weighs a pound. Duh, right? 

Then why do people keep claiming muscle weighs more than fat? It's because people confuse weight with volume. Muscle is more dense than fat. A pound of muscle takes up less space than a pound of fat, but when do you talk about your fat or muscle in terms of a specific volume? 

The easy solution is to stop saying, "Muscle weighs more than fat," and to start saying, "A pound of muscle takes up less space than a pound of fat." Or just avoid the topic altogether.

Group of adults running on outside trail
Flickr/John Loo

You need to be in the "fat-burning zone" to burn fat

This is just fundamentally untrue. 

Your body’s energy requirements operate on an upwardly angled line, more or less. As you move from sitting to walking to jogging to sprinting along the x-axis, your body's energy needs increase along the y-axis. Your body has to break down stored fat and carbohydrates (muscle glycogen and blood glucose) to produce this increased demand for energy. 

The thing is, your body doesn't break down just one source of fuel or the other -- it's constantly breaking down a ratio of the two. At lower intensities (say, sitting or walking), your body uses a greater ratio of fat to carbohydrate. Hence the name "fat-burning zone."

As exercise intensity increases, the ratio eventually flip-flops and you start burning a higher ratio of carbohydrates to fats. But since your total energy requirement has continued to rise, you actually burn more total calories and total calories from fats than you would during lower-intensity "fat-burning zone" training. So, for example, if you're burning six calories per minute at a 4:2 fat-to-carb ratio during jogging, you're still burning fewer fat calories than you would at a higher-intensity sprint of 11 calories per minute at a 5:6 fat-to-carb ratio.

Protein supplements are a requirement for muscle growth

PROTEIN is a requirement for muscle growth, but protein SUPPLEMENTS are not. The building blocks of proteins -- amino acids -- are absolutely necessary for muscle protein synthesis and repair after exercise, and protein supplements like protein bars and powders can, of course, provide the necessary amino acids. 

But you know what else can provide the necessary amino acids? Real food. Like chicken, tuna, eggs, milk, or vegetarian-friendly sources of protein, such as hemp, pea, or soy products. 

I’m not saying there’s no room for supplements, but believing you can’t see results in the gym without supplementation is like believing you can't go to work without stopping at Starbucks. One is not a requirement to successfully complete the other.

Lifting weights while pregnant will hurt the baby

As long as a woman was lifting weights prior to her pregnancy, and as long as her doctor clears her to exercise, there's no reason she can’t continue to train throughout pregnancy. This isn’t the Middle Ages, or even the 1950s. Women aren't dainty flowers, and pregnancy isn't an illness. 

In fact, women who prioritize exercise throughout pregnancy have easier labors and recoveries than those who don't. So, uh, yeah, lifting weights while pregnant can actually be a really good thing. Stop treating it like it’s a capital offense.

Muscular woman working out at the gym
Jacob Lund/Shutterstock

Lifting weights as a woman will bulk you up like a man

Good Lord, strength training will NOT turn women into big, bulky, or manly versions of themselves. It's true that testosterone helps promote muscle growth. As the male sex hormone, it’s a hormone that's abundant in men, which is one of the factors that makes it easier for men to put on muscle mass. 

Women have testosterone, too, and women's blood levels of testosterone also increase after strength training. But what you must understand is the levels of testosterone present in women, even after lifting weights, are SO MUCH LOWER than those present in men, which means that while women can add strength, they’re unlikely to develop a significant amount of mass without a very specific and intense training program. 

Man doing squats with weight
Uber Images/Shutterstock

Spot reduction is possible

If you think you can get six-pack abs by doing nothing but crunches, or a killer butt by doing nothing but squats, you're fighting a losing battle. 

Yes, you can gain strength and even develop muscle mass by performing exercises that target specific muscle groups, but unless your overall workout program is designed to help you lose the fat covering up those lovely, newly developed muscles, you’re not going to achieve the visual effect you're going for. 

If you have specific goals based on appearance, definitely train those specific muscle groups, but make sure you're engaging in a total-body routine that combines strength training, cardiovascular work, and a nutrition plan designed to support fat loss. It’s only through the loss of body fat that muscles will start to pop.

BMI and weight are good predictors of fitness

Yes, of course there are correlations between weight and BMI and disease risk, but as individual metrics, weight and BMI mean very little. They don't say anything about heart function, blood sugar, muscle mass, or bone health. They don't indicate how far you can run or how much you can lift. They're not so great at indicating body fat percentage or waist circumference, which are better predictors of internal health and disease risk. 

In other words, just because you have a "healthy" weight or BMI, doesn’t mean you have a healthy body fat percentage. Likewise, people with an “unhealthy” BMI can actually have a completely healthy body fat percentage. Weight and BMI are only helpful in relation to other health and fitness indicators. 

Girl laying face down on couch with remote controller

Muscle can turn to fat (or vice versa)

Muscle is a completely different tissue than fat. Your muscle won't disintegrate into fat if you stop going to the gym. Your fat won't develop into muscle by strength training.

You can gain muscle by strength training regularly and consuming high-quality proteins to stimulate muscle protein synthesis. At the same time, you can lose fat by creating a calorie deficit in your diet. Likewise, muscle can atrophy if you sit on the couch all day, and you can store more fat if you spend all that couch time munching on Cheetos.

Changes in muscle and fat mass often come at the same time because they correspond to certain lifestyle choices. This is why people assume that one tissue "turns into" the other, but they don't. It's completely possible to gain fat and muscle at the same time, or to lose fat and muscle at the same time. For most people, these scenarios aren’t ideal, which is why it's important to understand how the body works and how to make specific choices that support the body composition changes you actually want to achieve.

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Laura Williams is an exercise physiologist and fitness writer who used to believe (a long, LONG time ago), that muscle could "turn into" fat. Which fitness myths did you once believe? Share on Twitter: @girlsgonesporty.