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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?  

In this article, we will discuss the pros and cons of popular body composition methods and what they may mean for you! These methods have been validated either with respect to each other or with respect to an MRI. None of them see fat (though some get close), and for that reason, have inaccuracies. There's a ton of misinformation about accuracy and gold standards regarding body composition, so it may be helpful to review them here before getting started.

That being said, If used correctly, all of the below commercially viable methods can get within a ballpark estimate of an MRI, some as close as 2-3%. We break down the science, the user experience, ROI and ultimately aim to give you a more in-depth look at how to approach body composition. Let's dive right in!


7. Calipers

We all know this one. Those old “trusty” calipers. You’re not impressing anyone when you pull those out of a drawer. Even though they lack the sophistication of modern techniques, they still get a lot of play today. Why? Because of their size, ease of use, and frankly, they’re cheap! With that said, you get what you pay for! Don’t be fooled, it’s easy to make mistakes. Pinch someone (who’s clearly losing fat) in a different spot on a follow-up and all of sudden it looks like their body fat went up! 

How it works: Using the caliper’s tong-like features to pinch the skin in specific places, a licensed professional (recommended) or individual will record relative thickness of the skin fold. The areas selected for measurement are sex-specific as fat is stored differently in males and females. Chest, abdominal, and thigh are skin sites measured in men while triceps, waist, and thighs are the focus sites for women. The recorded data is then calibrated to a specific formula, which in turn produces body fat percentage.

The Science: The caliper method rests on the assumption that 50% of body fat rests under the skin. Measuring the thickness of skin folds where fat is most prevalent on the body will tell you how much fat to lean mass an individual has. 

Pros: Calipers are by far the cheapest and most mobile version of determining body fat composition. Good for understanding general range of an individual’s body composition.

Cons: While a cost-friendly and simple option for measuring body composition, calipers are most prone to human error and consequently have difficulty tracking precise body fat changes over time. To get accurate and precise results, you need to be extremely careful in how you measure the body, which is time consuming and labor intensive. You also need to make sure the same person is measuring your client throughout their journey to ensure consistency. With all these constraints, expect a margin of error of 10%.

User Experience: Nobody likes getting pinched. Period. Also, your wellness customers, obesity patients, or fitness members have come to expect at least a minimum level of technology when it comes to assessment- especially with the advent of wearables and other fitness trackers. You’re not impressing them by pressing them. 

ROI: Although they’re cheap, there isn’t a ton of value here. If you measure incorrectly, you could lose customers, and in turn, lose money. 

Bottom line: Look elsewhere- it’s time to invest in some technology. 

Our Grade: D-


6. 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 Science: 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.

How it works: Body measurements are taken manually at designated areas with measuring tape. This measurement process is repeated three times. The average of the three measurements taken at each spot is then input into a formula to calculate an individual's body composition. 

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. 

User Experience: 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!

ROI: Powerful method, but not much ROI if you measure incorrectly.

Bottom Line: The science is sound, but the instrumentation is lacking in sophistication. If paired with digital circumferences, like those from body scanners, then this method can be the new gold standard, and for that alone, it gets a better grade than Calipers. 

Grade: C


5. Hydrostatic Weighing:

Commonly referred to as the “dunk tank”, this is another old-school method for measuring body composition. But unless your clients are looking for a deep-sea adventure then this is not the best of experiences. The body composition results yielded are pretty accurate. BUT, the space requirements are impractical. Often third-party companies will drive around truck with a dunk tank inside, and charge a fee for the assessment. Convincing members to get wet though, is not an easy challenge to overcome. 

How it works: An individual is weighed on dry land and then slowly submerged on a scale into a tank of water. The individual will then expel all air from his or her lungs while their underwater weight is taken. The underwater weight is then compared to dry land weight and, using a specific formula, determines a person’s body composition.

The Science: Hydrostatic weighing, is based upon Archimedes Principle , which says that that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. In other words, denser material (i.e. lean muscle and bone) will weigh more underwater than less dense material (i.e. fat tissue). Pretty smart eh?

Pros: Hydrostatic weighing yields quite accurate body composition results if done correctly. Always a plus!

Cons: Ah yes the downsides. Results may be compromised if an individual does not literally breath out every last breath (gah!) - a process that may be difficult for some (imagine this after a hard workout), especially more vulnerable populations, to accomplish.

User Experience: Good for Pisces who love water. Bad for everyone else who doesn’t.

ROI: If you and your customers are serious about results, then reaching out to a service that provides hydrostatic weighing is a good investment. It’s a great value add and a memorable experience.

Bottom Line: Accurate, and not a ton of room for error. But the user experience is not great. Moreover, it’s not something you can include in your facility on a permanent basis. There may be better options for you.  

Grade: B


4. Air Displacement Plethysmography (ADP)

With ADP, it is important to breathe (literally) and not be intimidated by the name! Really, ADP is much like the dunk tank method (minus the scuba diver experience) and will have you noticing “something in the air”.

How it works: Individual enters a small chamber-like structure. At this time, changes in chamber pressure are recorded to determine body volume.

The Science: ADP uses one’s body mass and volume to gauge body density. The method uses air instead of water to measure volume. Using those density readings ADP then calculates the proportions of lean to fat mass (i.e. body composition).

Pros: ADP’s easily accessible chamber and non-invasive method make it great option for more vulnerable communities such as the elderly, children, and those with physical handicaps.

Cons: There are many variables (including hydration and body temperature) that can cloud ADP’s body composition results; these variables can make it difficult to receive an accurate reading especially for the active gym population who are often being tested pre and post-workout. The last thing we want is for our workouts to interfere with our readings. It’s why we’re being evaluated in the first place!

User Experience: Claustrophobic much? ADP is definitely not good for those who hate enclosed spaces. However, if you have people willing to “brave the cocoon” the process is pretty easy and non-invasive. There's also the not so fun hair cap you need to wear to get consistent results.  

ROI: Very accurate, but much better for an academic or medical setting. You might have more trouble trying to sell it as a value-add in a commercial setting like a health club. 

Bottom Line: Quite expensive, takes a lot of space, but if controlled correctly, can be quite accurate. 

Grade: B-


3. 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!

How it works: 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. 

The Science: 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.

User Experience: For those who like a quick and painless process (aka all of us) this is a great option. Just don’t down that massive electrolyte water before hopping on if you want accurate results!

ROI: Portable. Easy to use. Can be easily monetized as a value add. A great investment. 

Bottom Line: 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. 

Grade: B+


2. Dual-energy X-ray absorptiometry (DXA or DEXA)

Aside from sounding like a character from X-men, the DEXA scan is definitely a medical standard in measuring body composition.

How it works: The individual lies down on the exam table as the DEXA scanner moves over them. This process takes about 15 minutes and makes you feel like you’re in a cool Sci-Fi movie.

The Science: The DEXA (duel-energy X-ray absorptiometry) scan, originally focused on measuring bone mineral density, is now widely used as tool to measure body composition as well. DEXA accomplishes this by running two beams of light over the bone and gauging how much light is absorbed. The denser the material (i.e. more muscle to fat) the less the beams will be able to penetrate to the bone. This reading is then converted into a body fat percentage.

Pros: Accurate results; Measures bone density as well as body composition. Probably the most well validated body composition method in the academic world, other than the MRI. 

Cons: While incredibly precise, the DEXA system is expensive, often as high as $100k. DEXA scans you with X-rays, which can be harmful to your health if your exposure is too frequent. 

User Experience: Let’s face it. We all love laying down and relaxing while being assessed. But X-rays are dangerous, and there's some convincing to do to get people scanned. 

ROI: The most expensive choice on this list, it’s not the most practical investment for a facility. Third-party assessment services are offering DEXA scans as a service, which is becoming more common. Hiring a third-party and building it into a wellness program, fat-loss shred, inch-loss competition, or as a general value add could be a great way to increase membership sales and retention. 

Bottom Line: Amazing medical grade device and technology. Not so practical for most gyms and wellness centers given its size, price, and assessment process, but not a bad idea to provide as a service to members through a third-party service. 

Grade: A-


1. 3D Body Scanning

3D body scanning is one of the newest and growing trends in determining body composition. We love the way that it engages clients both visually and numerically. One of the key reasons why Body Scanning took first 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. 

How it works: An individual stands on a rotating platform with arms stretched out and hands in fists. The scan takes about 40 seconds (one full rotation) while a 3D image of the individual is being rendered.

The Science: 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. 

User Experience: Definitely ranks highly on the “personal space” scale as users do not have to be touched. Also, we love the quick assessment time and ability to see the body comp. output in 3D form. Those that are a little shyer about wearing tight or little clothing might feel uncomfortable rotating on a platform. Its recommended to create a private setting. 

ROI: 3D images speak louder than numbers and is a great way to engage and retain members. It is an awesome value-add for PT and wellness services. 

Bottom Line: Great innovative technology with precise results. Has the power to not only be an assessment tool, but also a sales and retention tool. Much easier to control for clothing requirement to get precise results, than it is to have to control for hydration with BIA or ADP. 

Grade: A-

So, there you have it! All the necessary information to make an informed and insightful decision regarding body composition measurement. Remember this and you should be on your way to a more effective and rich measuring experience.  

Raj Sareen

Written by Raj Sareen

Raj is the CEO and Co-founder of Styku, a 3D body scanning and body shape analysis system for health, fitness, and wellness professionals. He is also a physicist, with a background in extra-solar planetary astronomy and once worked in the Human Space Flight Program at NASA.