Exactly as it sounds, body fat percentage measures how much fat is stored in your body, says registered dietitian and certified strength and conditioning specialist Reda Elmardi, founder of The Gym Goat. It measures what percent of your overall body weight—the sum of your organs, skin, bones, fat, muscle—comes from fat.
“Body fat percentage is a better determinant of health than BMI,” says founder of Pandia Health Sophia Yen, MD, MPH. Unlike BMI which looks at a person’s overall mass compared to their height, body fat percentage allows you to look specifically at how much fat mass a person has, explains Matthew Scarfo, a NASM-certified CPT-OPT with Lift Vault. As such, “it’s a measurement that allows doctors to provide more individualized care,” he says.
What is considered a healthy body fat percentage?
What qualifies as a healthy body fat percentage varies based on factors such as age, sex, genetics, lifestyle, overall health, and activity level, according to Elmardi. For people assigned female at birth, a normal body fat percentage range is between 18 and 30 percent, he says. Per the American Council on Exercise, female athletes (especially of the professional variety) can safely hover within the 14 to 20 percent range.
As a general rule, cisgender women need more essential body fat compared to cisgender men, who can safely hover between 6 and 24 percent body fat. Why? Put simply, child rearing, says Yen. “If you don’t have enough fat, then your body says 'well this person doesn’t have enough nutrients to sustain a pregnancy,'” she explains.
The risks of having a higher or lower body fat percentage
People assigned female at birth are considered medically overweight if they are above 30 percent body fat and underweight if they are below 14 percent.
While someone can have a body fat percentage over 30 and not have any health problems, “over time, your risk for a number of conditions such as high blood pressure, diabetes, heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea, and certain types of cancer increases,” Elmardi says.
Still, this is not a case of the lower the better. A body fat percentage under 14 can present its own health risks. “Body fat is the body's natural storage of energy,” explains Elmardi. “You need some of this fat to fuel your heart beating, your brain functioning, and your muscles working,” he says. If you don't have enough, your body won’t be able to function optimally.
Visceral body fat (the kind stored around the organs) also produces hormones. Having too little can lead the body to make less estrogen, which can impact a person’s menstrual cycle. In some cases, low body fat can halt a person’s cycle altogether and they won't ovulate, says Dr. Yen. Low body fat during pregnancy has also been linked with higher rates of miscarriage.
Body fat is also essential for absorbing fat-soluble vitamins, like A, D, E, and K. As such, too low body fat can result in nutritional deficiencies that lead to fatigue, dizziness, mental fog, achy joints, or changes in hair or skin texture.
So… should I be tracking my body fat percentage?
Typically, your body fat percentage is useful information to know, says Hannah Daugherty, a certified personal trainer with Exercise With Style. “Even if the estimate is a rough one, knowing where you stand can shed some light on your health, and can help with health and fitness goal setting and future outlooks,” she says.
General wellness aside, due to the link between body fat percentage and menstrual cycle, people who eventually want to become pregnant and those having difficulty with fertility may choose to track their body fat percentage to make sure that it’s high enough to support a healthy flow.
It can also be a useful measurement for athletes to keep track of, in particular pre-menopausal athletes who have ever lost their menstrual cycle, says Daugherty. Low body fat is not the sole cause of amenorrhea—the medical term for an MIA menstrual cycle—but low weight and body fat can increase the risk, she says.
Additionally, healthcare providers may also choose to measure the body fat of individuals who have persistent vitamin deficiencies, as well a crop of symptoms commonly associated with malnutrition such as fatigue and hair loss.
But, body fat percentage is not a good measure for everyone to keep track of. If you have a history of disordered eating, body dysmorphia, or orthorexia, monitoring your body fat percentage can lead to unhealthy mental, eating, or exercise patterns. In this case, taking note of symptoms commonly associated with too low or too high body fat percentage is sufficient.
Exactly how to measure body fat percentage
If you’re interested in learning your body fat percentage, you’re probably wondering how the heck you can do that. There are a number of mechanisms and machines that are designed to spit out a number. Which you opt for will depend on whether or not you’re willing to go into a health or fitness facility, as well as what margin of error you’re willing to accept.
The most accessible method is the calipers skinfold test which is an old-school assessment that involves using a caliper (basically, giant metal clothespins with a little dial attached) to pinch skin and fat on a number of different body parts, including the triceps, biceps, shoulders, and hips. While this test is an okay way for assessing where you hold your subcutaneous fat, it usually low or high balls your total body fat by a significant 3.5 to 5 percent.
For people who want to gauge their body fat right from home, a better option is smart scale, which looks like your run-of-the-mill bathroom scale, but provides measurements such as water weight, bone density, BMI, muscle mass (sometimes even muscle mass per limb!), and body fat percentage. The jury is out on how accurate these scales are. One very small study suggests not very, but Daugherty says they provide a rough enough estimate.
Finally, if you’re willing to go to a doctor’s office or fitness facility for a test, there are also 3D body scanners, air displacement plethysmographs, and under-water weighing, to name just a few modalities. These are all considered to be quite accurate, but usually cost a pretty penny (or 10).
Of course, no single number tells the whole story. The other measures you track will vary based on your overall health and fitness goals. But generally speaking, how much you can lift, how fast you can move, how long you’re sleeping, heart rate variability, and heart rate all offer valuable qualitative insights to your health.
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