The Most Accurate Methods to Calculate Your Body Fat Percentage
To maintain a proper weight and good health, it’s important to keep close track of your body fat. Over the years, there have been countless ways to measure this metric; differing in cost, accuracy, and execution.
It all started in 1832 when a social scientist was looking for a way to explain the differences in the sizes and shapes of the human body. Thus, the first way to measure fat was developed with what is still known today as the Body Mass Index, or BMI.
In this article, we’ll look at some of the current methods available to measure your body fat, the accuracy of each, the general costs, and more—helping you choose the technique that works best for your body shape and size.
Body Mass Index (BMI)
Let’s start with the most common and well-known way to measure your body fat. This figure is calculated from your height and weight, and is a good gauge for the risk of diseases that occur with more body fat.
The higher your BMI, the higher the risk for heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.
If you have a muscular build, it may overestimate the body fat percentage. It can also work to underestimate body fat in older persons, or those who have lost muscle. The formula doesn’t take age or gender into consideration, which can affect the results (i.e. women have more body fat).
A recent study showed that, according to BMI, the average NFL linebacker would likely be categorized as “obese” and the world’s top sprinters (who have about 8% body fat) would score as being at least a bit overweight.
Unfortunately, despite inaccuracies, insurance companies still use BMI to raise premiums. Nevertheless, there are other proven ways to measure body fat that are just as (if not more) effective.
A new paradigm for measuring body fat looks at the total composition of the body in general. Body composition is the measure of fat mass to lean tissue. This includes:
There are dozens of ways to measure body composition, ranging from quick and easy to incredibly detailed. These techniques can help an individual set baseline values for fitness and health goals later down the line.
Relative Fat Mass Index (RFM)
This method uses the waist-to-height ratio which says that if your waist circumference is less than half your height, it’s a good sign you are fit. New studies have shown that RFM is a much more accurate predictor of body fat than the BMI ratio and it can also be worked out using just a tape measure. There’s no scale necessary!
Based on data from 3,456 adult patients in the United States, RFM measurements closely matched those taken by a high-tech DEXA body scan (widely considered the gold standard). RFM is also one of the most inexpensive ways to measure body fat out there.
A highly accessible method for measuring body composition is through the skinfold assessment, which can be done using either three, four, or seven sites on the body.
In this method, the specialist pinches the skin with a caliper to measure the thickness of the fold. After plugging the numbers into a formula, practitioners can get an estimate of total body composition.
This method is relatively inexpensive (calipers run about $10) and can be completed in a matter of minutes. However, body fat distribution will affect the results. A participant that holds greater fat outside of the measured area might end up with a lower reading, so keep that in mind.
Experts agree that the most accurate way to measure body fat is through a test known as DEXA, which stands for “Dual-Energy X-ray Absorptiometry.” This is an x-ray that is often used by sports teams to assess an athlete’s health and yields an exact measurement of body composition, including fat, bone, and muscle. It can also show muscle imbalances and bone mineral density.
In this test, participants lie on a table while an x-ray arm passes over the entire body, emitting a high and low-energy x-ray beam. Technicians then measure the absorption of each beam to get accurate readings of lean body mass and fat mass.
Since the machine also scans body parts separately, it can even break down the results by limb. Always thought your right leg was stronger? Now you can find out.
Just keep in mind that DEXA scans are typically not covered by insurance and can run patients anywhere from $150-$1,000 per test.
Don’t let the name of this test scare you. Subjects don’t feel a thing! Bioelectrical impedance scales range from simple to complex. Normal scales will have electrodes under each foot, while the more involved scales have handholds with additional electrodes.
The device works by sending tiny electrical impulses through the body, and then measuring how quickly those impulses return. Since lean tissue conducts impulses quicker than fatty tissue, a faster response means a leaner physique.
Although this form of measurement is quite affordable, there are many factors that can lead to inaccuracy. Variables like hydration levels, mealtimes, and workouts can all affect the type of reading you take. For the most consistency, you should use bioelectrical impedance at the same time every day, in the same conditions.
Don’t mind being dunked underwater? Then this method might suit you. Also referred to as “underwater weighing”, this system compares a subject’s normal body weight (outside of water) to their weight while completely submerged.
These two numbers, along with the density of the water, can accurately nail down a subject’s density. This number is then used to calculate body composition.
For many years, hydrostatic weighing was touted as the top scale for measuring body fat.
However, it is not able to account for bone density. As a result, it tends to overestimate with
older adults who have low bone density, and underestimate body fat in athletic individuals with high bone density.
It may also be difficult to find a lab that performs this type of body fat measurement. The procedure costs anywhere from $40-$100 and is somewhat uncomfortable. Subjects must force all of the air out of their lungs and sit submerged, completely underwater, for some time.
The latest and greatest in scales can also help you to better guestimate your body fat. Certain white-glove brands, like Naked and ShapeScale, use infrared technology to create a 3-D avatar that will demonstrate fat/muscle displacement. And unlike a DEXA, this can all be done in the comfort of your own home.
These smart scales even allow people to target specific goals, like building pecs or glutes. You can then compare your past and present avatars for a visual representation of success. The scales will also show you imbalances you may need to address and exactly where you have to fight fat on your body.
Body Volume Indicator
A body volume indicator compares your total body volume with that of your belly. This is essentially measuring your ratio of total body fat to visceral fat. Using a BVI app, a physician can measure your body volume indicator by entering vitals such as:
- Level of fitness
The app will also ask for front and side profile photos. The technology then divides your body into seven 3-D slices to further analyze body volume and composition.
In less than 30-seconds, you will have a measurement of the volume of body fat, visceral fat, abdomen volume, waist-to-hip ratio, BMI, and your unique BVI number.
Air-Displacement Plethysmography (BOD Pod)
This technique is very similar to underwater weighing, except it uses air. First, participants sit in a small machine, which then measures how much air is displaced. This will allow technicians to quickly determine body density. This is then used to calculate body composition.
This method is slightly more comfortable than the water technique, but it’s not something likely found in your neighborhood gym. The cost can also run anywhere from $40-$100 for a single session.
The Future of BMI and Weight Assessment
There are always ways for humans to measure their bodies and calculate ratios. Magnetic resonance imaging (MRI) and computerized tomography (CT) scans are the most accurate methods to date for assessing tissues, organs, and your entire body fat mass (including muscle and bone).
Every day, new methods are being invented that are smaller, cheaper, and more convenient than the current programs we have.
Regardless of which modality you choose, it’s important to wait 6-8 weeks before retesting with the same procedure. You should also stick to one main technique so as not to overcomplicate the results. Although skin calipers are slightly less accurate than underwater weighing, they’re way more affordable. The idea is that you are using these tools to stay on the right track.
After testing, start to examine things like lifestyle, diet, medications, age, supplements, and other factors to see where changes can be made. Keep in mind that your body fat percentage is only one data point in the metrics of your health. It is not a measure of self-worth or aesthetics, but ultimately how you feel.