What You Need to Know about Your Body Fat Percentage

When athletes or celebrities show off their bodies, signs of awe about their sculpted shapes typically revolve around this comment: “She (or he) has a body fat percentage of only six percent.”

In fact, the now-famous six-pack abs usually require a relatively low body fat percentage. But does a low body fat percentage provide a clear picture of a healthy person?

How about Body Mass Index (BMI)? Does that more easily calculated number provide an accurate snapshot of a person’s health? According to the CDC, “Body Mass Index (BMI) is a person's weight in kilograms divided by the square of height in meters. A high BMI can be an indicator of high body fatness. BMI can be used to screen for weight categories that may lead to health problems but it is not diagnostic of the body fatness or health of an individual.”

However, BMI does have some quirks. For example, if you are normal weight according to BMI, you can still be obese, primarily due to low levels of lean muscle mass.

For a few who are classified as obese according to BMI, their lean muscle mass and low body fat percentage make them outliers in the BMI classification since these people are typically high-level athletes or dedicated weekend warriors. Think of the NFL running back who is five feet nine inches tall and weighs 220 pounds. His BMI would be 32.5, placing him squarely in the obese category. But one look at this running back in the weight room and the inability of 300 pound men to tackle him makes that definition of obese irrelevant.

Muscle memory

Muscles primarily help with movement, maintaining posture, and supporting bodily functions.

The body’s collective muscle tissue constitutes its muscle mass. Usually, the term “muscle mass” specifically refers to skeletal muscle. This is the only type of muscle that a person can voluntarily control. Skeletal muscle plays a key role in movement. For example, bending the arm upward requires the bicep muscle to contract and the triceps to relax.

Exercising the skeletal muscles in various ways can increase the body’s mobility, balance, and strength. Keeping the skeletal muscles healthy is important for daily functioning. This may be particularly important for older adults since they tend to lose muscle mass in their later years.

In addition, people are defined by these three body types. An ectomorph is a typical skinny guy. Ecto’s have a light build with small joints and lean muscle. Usually ectomorph’s have long thin limbs with stringy muscles. Shoulders tend to be thin with little width.

A mesomorph has a large bone structure, large muscles and a naturally athletic physique. Mesomorphs are the best body type for bodybuilding. They find it quite easy to gain and lose weight. They are naturally strong which is the perfect platform for building muscle. The endomorph body type is solid and generally soft.

Endomorphs gain fat very easily. Endo’s are usually of a shorter build with thick arms and legs. Muscles are strong, especially the upper legs. Endomorphs find they are naturally strong in leg exercises like the squat.

All three body types affect body fat percentage and BMI. For example, an effective muscle-building program for ectomorphs would include more weight training since too much cardio tends to increase fat loss without a muscular body to uncover underneath of it all.

Diet and muscle mass

So here’s how BMI and body fat percentage can interact in some puzzling ways. Beginning a calorie-restrictive diet can, of course, decrease a person’s weight and consequently that person’s BMI.

That’s good.

However, restrictive diets also tend to reduce lean muscle mass, leading to a higher body fat percentage.

That’s bad.

“Skinny fat” people often have the outward appearance of health but without the corresponding internal muscular scaffolding. However, too much of anything can be detrimental to a person’s health. Men with a body fat percentage below eight percent can offer suffer from low energy, heart problems and being cold all the time. For women, that threshold is 14 percent.

When dieting, nutritionists recommend a balanced diet with lean protein, healthy carbohydrates, water and exercise. Follow those simple rules can help a person lose weight and maintain muscle mass.

Calculating body fat percentage

The most accurate ways to calculate body fat percentage involves expensive medical equipment. For example, it is possible to calculate muscle mass percentage from an MRI scan.

However, it is also possible to estimate muscle mass percentage at home. While many online calculators and tools claim to do this, it is unclear whether any of these methods are accurate.

Most rely on calculating body fat percentage. Subtracting this percentage from 100 will leave the percentage of lean body mass.

There are several ways to determine body fat percentage at home. For example, a person can use a body fat scale, which calculates the amount of fat by sending an electrical current through the body.

The United States Navy recommend a different method, which involves measuring the circumferences of various body parts. These add up to a certain value, and different values and heights represent various body fat percentages.

A basic way to measure body fat percentage is by using a soft tape measure, like the kind you’d use for sewing, to record measurements of different parts of the body. You can also find tape measures specifically marketed as body fat tape measures. For this method, you’ll also need to know your height in inches.

For men, measure the circumference of your neck and abdomen. Make sure you measure the largest part of each area. It may be easier to have a friend or family member help.

To calculate body fat percentage, subtract your neck value from your abdomen value to determine your circumference value.

For women, you should record a measurement of the circumference of your neck, natural waist, and hips. Remember to measure each area at the widest part. You may want to ask a friend or family member to help.

To calculate body fat percentage, add your waist and hip measurements, and then subtract the neck measurement to determine your circumference value. For example, if your waist is 30, your hips are 36, and your neck is 13, your circumference value would be 53.

When the tape is placed over the skin, it should make contact but not compress the skin in any way. Take all measurements twice and average them. Then record to the nearest half inch. If you can’t find the corresponding chart, you may consider using an online Navy Body Fat Calculator to obtain your estimated body fat percentage.

Fancy measurements

As previously stated, The most accurate ways to calculate body fat percentage involves expensive medical equipment. Here are a few to consider:

Calipers – A skin-fold test is done using a tool called calipers to pinch different areas of your body and measure body fat. There are a few ways to measure, but many people go with a three-site approach developed by researchers Jackson and Pollock in the 1980s. This method takes the least amount of time to complete. It’s also cost-effective, as you can find calipers online for less than $7.

Bathroom Scales - Your bathroom scale may estimate your body fat as part of its various functions. Body fat scales use technology called bioelectrical impedance analysis (BIA). When you step on the scale, an electrical current passes through one leg, up to the pelvis, and down the other. Fat conducts far less electricity than the water and muscle you have in your body. So, when the scale picks up more resistance, it records more possible body fat.

Combined with your entered height, weight, age, and gender, the scale then uses an equation to provide your body fat percentage.

Hydrostatic weight - is a weighing method where you sit undressed in a chair that’s submerged in water. Your body density or weight under water is recorded as your body places a buoyant counterforce on the water and displaces it. The weight recorded can then be used to calculate your body fat percentage.

Underwater weighing for body fat percentage is highly accurate and considered the gold standard for measuring body fat percentage. The percentage that it estimates should be within one percent of body fat for both adults and children. It’s much more accurate than at-home methods, like skinfold and bioelectrical impedance.

You’ll need to go to a special facility to have your weight recorded this way. You also may not like having a test under water. And not all insurances cover the total cost of this type of test.

MRI or CT scans – Perhaps the most accurate (and the most expensive) method for determining body fat percentage is with magnetic resonance imaging (MRI) or computerized tomography (CT) scans. These machines take cross-sectional images of the body and can even measure intra-abdominal fat. These tests are not often used for the sole purpose of measuring body fat.

Body fat percentage ranges

The American College of Sports Medicine has shared guidelines for body fat percentage by sex and age.

Age

20–29 7-17% (Male) 16-24% (Female)

30–39 12-21% (Male) 17-25% (Female)

40–49 14-23% (Male) 19-28% (Female)

50–59 16-24% (Male) 22-31% (Female)

60+ 17-25% (Male) 22-33% (Female)

Final thoughts on fat

Unfortunately, BMI numbers are much too generalized to be truly useful. These numbers were developed using data from enormous numbers of people. They don't tell you anything about your own body composition, how much of your weight is fat, and how much is muscles and tissue.

While BMI is a broad, general measure of risk, body-fat assessment is much more specific to your actual fat content and thus provides a more accurate picture. Use the methods described above to calculate your body-fat percentage then compare that score to the guidelines and develop a nutrition and exercise program that accounts for both your body type and your body fat percentage.

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