Body fat in the fitness industry is often a controversial topic. However, with the right tool, measuring body composition can be a powerful way to engage individuals with a personal training program, demonstrate progress, and retain members. So, which tool is best for you?

1. Skin Calipers

It might not be St. Patrick’s Day, but get ready to be pinched! Perhaps the most accessible method for measuring body composition, technicians perform a skin fold assessment using either three, four or seven sites (meaning parts of the body). The technician doing the test first pinches the skin. Then, he or she uses the skin caliper device to measure the thickness of the skin fold for each site. Each protocol has specific sites for testing, commonly including the chest, arms, abs and thighs. After plugging the numbers into a formula, practitioners can estimate body fat percentage.

Pros: Since calipers are relatively inexpensive (about $10 per pair), the skin fold method is the most easily accessible of all the methods listed here. Most gyms will have a pair handy. And you can expect more than a few trainers on staff to have adequate experience using them. Eager to keep close tabs on your progress? Consider investing in a pair of calipers for at-home testing. (Remember though, it does take considerable practice to be able to accurately self-administer the test.) Bonus: A proper skin fold assessment can be completed in just a matter of minutes, any time or place.

Cons: This method relies on readings from only a handful of body parts, so margin for error can vary. This highly depends on the experience and knowledge of the technician. To minimize error, the most important thing is to use the exact same spots every time. Consistency with calipers takes practice, so the key is to practice a lot — or find an expert technician” Body fat distribution can factor into the accuracy level as well. Although the test takes a measurement from each main area of the body (including the upper body, midsection and lower), a participant that holds greater amounts of fat outside of the measured areas might end up with a lower reading.

2. DEXA (Dual-Energy X-Ray Absorptiometry)

Think X-rays only detect broken bones? A DEXA scan exposes patients to X-ray beams of differing intensities. And experts use it to measure bone mineral density alongside body composition. Participants lie still on a table while a machine arm passes over their entire body. This arm emits a high- and a low-energy X-ray beam. By measuring the absorption of each beam into parts of the body, technicians can get readings for bone mineral density, lean body mass and fat mass. Also, because the machine scans body parts individually, the test can also break down body composition per limb. That means you can confirm suspicions that your right leg is indeed just a bit stronger than your left.

Pros: Like hydrostatic weighing, DEXA scans are incredibly accurate at measuring body composition. Whereas hydrostatic weighing involves dunking under the water, a DEXA scan simply involves lying on a table for a few quick, dry and painless minutes.

Cons: Like the hydrostatic weighing method, don’t count on around-the-clock availability of DEXA’s advanced technology. Getting a DEXA scan usually involves making an appointment with a medical professional. The high level of accuracy also comes at a relatively high price tag (which will vary by location) compared to other methods.

3. Hydrostatic Weighing

If the thought of getting dunked underwater suits your fancy, this might be the method for you. Hydrostatic weighing, commonly referred to as underwater weighing, compares a subject’s normal bodyweight (outside the water) to his or her bodyweight while completely submerged. Using these two numbers and the density of the water, operators can accurately nail down the subject’s density. This number is then used to estimate body composition.

Pros: Hydrostatic weighing is an incredibly accurate technique for measuring body composition. The technique uses tried and true variables that feature a low percentage of error. For that reason, many experts refer to hydrostatic weighing as the gold standard for measuring body composition. It’s also commonly used in research settings.

Cons: Unless you happen to have an underwater scale at home, you’re going to have to find a lab or a performance center for this. As a result, this method can be a bit inconvenient. It’s more expensive (ranging from $40 to $60) compared to other techniques, too. Subjects also have to forcefully exhale as much air out of their lungs as possible to reduce potential for error and sit submerged completely underwater. This might be uncomfortable for some individuals.

4. Air-Displacement Plethysmography

Don’t let the name intimidate you. Air-displacement plethysmography is actually very similar to underwater weighing. First, participants sit in a small machine, like this “BOD Pod.” Then, by measuring how air displacement by the individual, technicians can determine body density. Like underwater weighing, the participant’s body density is then used to calculate body composition.

Pros: Since the air-displacement plethysmography method doesn’t involve dunking your head underwater, many subjects will find it more comfortable. The shape and size of the machine used in this technique, which typically resembles an egg, makes it accommodating for almost any age, shape and size.

Cons: Along with DEXA and underwater weight, you won’t find air-displacement plethysmography in your neighborhood gym. While commercial machines might pop up at select high-level training facilities, locating one near you might be difficult. The cost (between $45 and $60 per reading) might also steer you in the other direction.

5. US Navy/Circumference Method:

Another common and cost-effective way to measure body composition is using a tape measure to calculate circumferences in regions where fat resides. In fact, the method so common that the entire US Armed Forces uses the method to measure body composition. Like calipers, the idea is quite straightforward: as people put on fat, they tend to expand in various regions of the body. Like calipers you can measure this expansion. Unlike calipers there’s no pinching involved. However, using the tape measure can be uncomfortable for your member or patient. Often, the biggest obstacle though is the lack of repeatability, a result of the difficulty of finding the same spot twice when taking a measurement. The US Navy or circumference method relies on running specific body measurements through a highly developed formula to produce body fat percentage. These measurements are taken manually at the abdomen and neck for men and at the neck, waist, and hips for women. During its research and development stage, this formula was calibrated using data from DEXA scans and, when administered correctly, is said to produce the same amount of accuracy.

Pros: Very easy to use and administer on site. The formula is highly reliable when done correctly.

Cons: Prone to human error as the method relies on taking measurements manually. Tilt the tape measure slightly, or add a bit of slack, and you’ll find extremely varying results. In fact, the margin of error can be as high as 10% just due to human error in measuring with a tape. Pretty painless experience for most but can be time consuming. For those that prefer not to be touched during assessment this method might not be so pleasant- especially since each measurement must be taken 3 times. That’s a lot of touching!

6. Bioelectrical Impedance Analysis (BIA)

Bioelectrical impedance (BIA) puts the buzz in body composition measurement with its internal electrical calculations. BIA devices are incredibly mobile and can be used in a variety of different spaces, which makes them optimal for small gyms or wellness centers. However, beware of accuracy after chugging that Gatorade post-workout!

An individual stands on a platform and wraps their hands around the two available handles. For about 20 seconds a small electrical current runs up both legs and arms. Some systems only have arm holds.  Bioelectrical impedance runs a small current of electricity through the body to gauge body composition. The method relies on the currents to easily permeate a cell’s membrane. Resistance to the current (from water) is a function of how hydrated your body is and is correlated with your body fat%. Like other methods, BIA doesn’t explicitly measure fat, but rather it infers body fat from a direct measurement of something else, in this case water.

Pros: BIA is a quick procedure compared to length of DEXA (15 minutes) and the repeat “dunks” of hydrostatic weighing. Additionally, like the 3D body scanning method, the device is easily movable. It is also fairly simple to run a BIA machine without the assistance of a professional.

Cons: Like Air Displacement Plethysmography, variables such as hydration amount can compromise the accuracy and precision of results. This again makes BIA difficult for athletes or gym-goers who are looking for the most optimal body composition results. Electrical currents also make BIA unsuitable for pregnant and pacemaker populations.

A great option for mobility, size, and relatively accurate body comp. results. However, be aware of the variables that can skew results and set expectations with members or clients appropriately. Moreover, there’s a big range of devices in this category that range in price and accuracy. So choose wisely.

7. 3D Body Scanning Method:

3D body scanning is one of the newest and growing trends in determining body composition. It engages clients both visually and numerically. One of the key reasons why Body Scanning took top place is the fact that it builds on the power of the caliper and circumference methods, without the human error. Like calipers and the circumference methods, 3D body scanners (body surface imaging technology) is the most direct measurement of body fat you can have without taking an MRI. But not all body scanners are built the same. Be careful to ensure that the digital tape measurements your body scanner of choice uses is precise. Often body scanners can appear visually accurate, but the circumferences be incorrect if the algorithms for determining the location of a waist, for example, are not consistent.

Using non-invasive 3D cameras, body scanning captures surface data of an individual and renders an exact 3D model. This is accomplished with harmless infrared light that reflects off the body, but is invisible to the eye. Digital measurements on the surface of the body are then taken that replicate a tape measure, but are without the imprecision of human measurements. Additional measurements, such as volume and surface area can be calculated from the 3D model. These measurements are then used to calculate body composition. The science here is so promising that the NIH just approved a multi-million-dollar grant to two leading body composition institutes to test body scanners further, and stating that a key motivation is the belief that body scanners hold the most promise for commercial appeal and reliability.

Pros: The 3D Scanner is easily transportable and, like BIA, only takes a short amount of time. 3D body scanning also captures precise measurements with camera technology, which lessens the amount of human error (as seen with calipers) and allows for accurately tracking composition changes over time (much like DEXA). The 3D visuals are extremely engaging and becomes a great conversation starter. Many gyms will use 3D body scanning as a customer acquisition tool to demonstrate the sophistication of their services. 3D scanning is also a great educational tool. Often explaining what body fat is difficult, but visually showing someone how their body is changing with metrics that are easier to understand (like waist circumference) helps them connect the dots. That’s especially important if their total weight is not changing, but their shape is transforming.

Cons: Because 3D body scanning uses a non-invasive and surface-only camera, individuals wearing baggy or loose-fitting clothing will not elicit precise results. Therefore, subjects must wear form fitting clothing. This tends to be an easy ask for women, as women are often wearing compression garments such as Pilates/yoga pants. Men, however, don’t usually own compression shorts.