And FYI: The number on the scale here really shouldn't matter.

By Lauren Bedosky
May 18, 2020
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There's a saying you've likely heard before: "Muscle weighs more than fat"—and while many may think it's a trick question, it's not. (Though it is similar to "What weighs more, a pound of feathers or a pound of bricks?" That is, in fact, a trick question—a pound weighs a pound, regardless of the material.)

Overall, the question of whether muscle weighs more than fat hinges more on the size of what's being weighed—taking it back to the bricks versus feathers example, a pound of feathers will look much larger in size than a pound of bricks.

That's what's really at the root of this question: size—and for people, this centers on body composition, the proportion of fat versus non-fat mass in your body (which actually includes muscle, bones, and organs). While it should be said, first and foremost, that body size or weight is not necessarily an indication of health, there is some truth behind the saying that muscle weighs more than fat—here's what you need to know.

Does muscle actually weigh more than fat?

The short answer: Yes, to a certain extent muscle does weigh more than fat; if you simply take a bowl of fat and compare it to a same-sized bowl of muscle, the muscle will weigh more. But that's only an explanation in the simplest of terms—there's much more that goes into that question, particularly how your body responds to these two tissues, body fat and muscle.

Muscle can weigh more than fat because it’s denser, says Joel Seedman, PhD, neuromuscular physiologist and owner of Advanced Human Performance in Suwanee, Georgia. So, as previously explained, if you hold a fistful of muscle it will weigh more than the same fistful of fat because you technically have more of the compact tissue in your hand. The catch: That number on the scale shouldn’t really matter here, because the benefits of having more muscle tissue in the body outweighs having more fat tissue.

Credit: Getty Images - Animation: Alex Sandoval

How having muscle affects your health:

Muscle is a star player in keeping your body happy and healthy in the long-term, for several reasons. For starters, lean muscle mass can help manage blood sugar, keeping type 2 diabetes at bay. In fact, one 2017 cohort study published in PLoS One found a negative association between muscle mass and risk of developing of type 2 diabetes—specifically that a higher muscle mass meant a lower chance of type 2 diabetes. “The number one consumer of blood sugar in the human body is skeletal muscle,” says Tim Church, MD, MPH, PhD, professor of preventive medicine at Pennington Biomedical Research Center at Louisiana State University. So, the more muscle you have, the greater your potential to metabolize blood sugar. As an added bonus, the blood sugar-regulating effect is instant and lasting after exercise. So if you do a workout today, your muscles will utilize blood sugar better over the next 72 hours, Church says.

Also, as you age, you’ll want a healthy amount of muscle, rather than fat. “Muscle is a commonly overlooked marker of healthy aging,” Church says. You lose about 1-2% of muscle mass starting around age 40 or 45, he adds. This age-related decline in muscle is known as sarcopenia, and it’s one of the biggest reasons many older adults can no longer do simple tasks without help. “You can’t put your jacket on, you can’t push yourself off the toilet, and you can’t get yourself off the ground after you fall,” Church says. “It all comes down to strength and muscle mass.”

What’s even better news is that muscle can further help you maintain a healthy weight by raising your basal metabolic rate, or the number of calories you burn at rest. Exactly how many extra calories you’ll burn by adding muscle is unclear: “That number has been widely discussed and argued over the years,” says Seedman. “But we do know the more muscle you have, the faster your metabolism.”

Lastly—and least importantly, at least pertaining to health, the density of muscle might cause it to weigh more, it also means it takes up less space in the body. “If someone gains 10 pounds of muscle, a lot of times they’ll barely notice that on their body,” Seedman says, “whereas, if you gain five or 10 pounds of fat, you definitely notice that.” 

How having fat affects your health:

While fat is often demonized, you do need some body fat to survive (and even thrive). Fat tissue plays a few important roles, from regulating body temperature and producing hormones, to supporting brain health and insulating organs, says Church. According to the American Council on Exercise, healthy body fat percentages for women can range anywhere from 10% to 31%.

When you go over that number, that’s when fat can potentially become harmful to your health. “People think fat is just excess storage of energy, but it’s really the number one driver of inflammatory markers in your blood,” Church says. Chronic inflammation can also contribute to a wide variety of conditions, including type 2 diabetes, arthritis, inflammatory bowel disease, and obesity. A high body fat percentage has also been linked to heart problems. “There’s a strong correlation between higher levels of body fat and an increased risk for cardiovascular disease and a number of other health issues,” Seedman says.

How to measure your body fat and lean muscle mass percentage:

To get a sense of how much body fat versus lean muscle mass you’re carrying around, a bioelectric impedance scale will provide numbers. Many devices that use this technology look like an ordinary bathroom scale, but they measure your body composition through electrical impulses (don’t worry, you can’t feel it). According to the Harvard T.H. Chan School of Public Health, the electrical current faces more resistance when it passes through body fat than it does passing through lean mass and water. From there, the scale uses an internal equation to estimate your body fat and muscle mass. Unfortunately, the bioelectric impedance scale can be hard to calibrate for accuracy, as any change in water weight (say, if you’re dehydrated or have an illness) from one reading to the next may throw off the numbers.

Body fat calipers, also known as skinfold calipers, are another inexpensive tool to measuring your body fat percentage (some look like a big set of tweezers). Seedman suggests getting a fitness professional to take the reading, as they’ll have more practice getting a more accurate measurement. (You can also try this ACE formula for doing it at home, if you have skin calibers.)

If you want to keep tabs on your risk status for conditions like type 2 diabetes, high blood pressure and heart disease, measuring your waist circumference may also help give you a glimpse into your health, according to Church. If your waist measures more than 35 inches (for a non-pregnant woman), you may be at a higher risk for developing obesity-related health conditions. The CDC offers guidelines for taking accurate waist measurements. (Note, this doesn’t exactly tell you your body fat percentage, but will provide a glimpse into your health.)

The most common way most people measure body composition is through body mass index (or BMI). While the CDC offers an online calculator for figuring it out, it doesn’t take into account your body fat percentage—a major pitfall to BMI numbers, according to Harvard T.H. Chan. So, if you’ve packed on muscle through resistance training, your BMI score may give you an inaccurate view of your health status.

How to lose fat and gain muscle in a healthy way:

The smartest move for building muscle and cutting back on fat: strength training. “If you only have a limited amount of time to work out, strength training has been shown to be exponentially more powerful,” Seedman says. Plus, you can manipulate work and rest ratios to get more cardio benefits from your strength routine, he adds.

Seedman recommends doing a full-body strength routine at least twice a week, making sure to lift to the point of near-failure in each set—that means those last one or two reps should feel nearly impossible to do without breaking form. If you’re trying to shed fat while building muscle, keep the rest periods short in between sets (30 to 60 seconds) to crank up the intensity of the sweat session. Choose five to six exercises (three lower-body, three upper-body) and shoot for 3-4 sets of 6-12 reps per move.

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