Body Fat Testing
Written by Melissa Hurley
Are you overweight, skinny-fat or just curious about your lean body mass percentage? The easiest test to know if you’re healthy or not, and probably one of the most widely used, is called the Basal Metabolic Index. However, this testing method isn’t the best way to know if it’s time to lose weight and can actually be really wrong if you’re someone who works out regularly or are older in age. Thankfully, there are a few better ways to help us understand a little more on how the weight of our body is broken down. Body composition, which is the measure of fat mass to lean tissue (including bone, muscle, ligaments, tendons and organs), is an important metric that often gets overlooked.
There are dozens of methods to measure body composition, ranging from the quick and (relatively) painless to the incredibly detailed. These measurement techniques can help individuals set baseline values for body composition and goals for later on down the line. However, with the variation in methods comes a fluctuation in accuracy. One method might nail down your percentage of body fat to within a few decimals, while others leave a wider range of error. To help you understand the numerous techniques, below are the top five methods for measuring body composition along with the pros and cons of each.
The most accessible method for measuring body composition, a skinfold assessment can be done using either three, four or seven sites (meaning parts of the body). The technician pinches the skin and then uses the skin caliper device to measure the thickness of the skin fold for each site. After plugging the numbers into a formula, practitioners can estimate body composition.
Pros: Calipers are relatively inexpensive (about $10 per pair). This test is the most easily accessible of all the methods listed here. A proper skinfold assessment can be completed in just a matter of minutes, anytime or place.
Cons: Body fat distribution can factor into the accuracy. Although the test takes a measurement from each main area of the body (including the upper body, midsection and lower body), a participant that holds greater amounts of fat outside of the measured areas might end up with a lower reading. Human error is a factor, depending on the experience and knowledge of the technician and consistency with calipers takes practice, so the key is to practice a lot — or find an expert technician. The most important thing is to use the exact same spots every time.
Don’t let the name scare you; users won’t even feel a thing. Bioelectrical impedance scales range from the simple (a normal scale with electrodes under each foot) to the complex (a scale that has handholds with additional electrodes). Both devices work by sending tiny electrical impulses through the body and measuring how quickly those impulses return. Since lean tissue conducts electrical impulses quicker than fatty tissue, a faster response time is correlated with a leaner physique.
Pros: Bioelectrical impedance monitors tend to be affordable enough to keep one around the house. Since this technique requires little more than pressing a button, users need little to no previous practice, and measurements can be done in a matter of seconds.
Cons: Bioelectrical impedance measurements are generally less accurate than below methods. Readings can be greatly affected by variables like hydration levels (since water also conducts electrical impulses), mealtimes (a recent meal can skew results), and workouts (taking a reading directly after exercise leads to a lower body fat reading). For the most consistent reading, take readings at similar times during the day in the same conditions.
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 their 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.
Cons: You’re going to have to find a lab or a performance center that offers hydrostatic weighing, which can be a bit inconvenient and more expensive (ranging from $40 to $60) compared to other techniques. 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, which might be uncomfortable for some individuals.
DEXA (Dual-Energy X-Ray Absorptiometry)
Think X-rays were just for broken bones? A DEXA scan exposes patients to X-ray beams of differing intensities and can be used to measure bone mineral density alongside body composition. Participants lie still on a table while a machine arm passes over their entire body, which 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. And since the machine scans body parts individually, the test can also break down body composition per limb so you can confirm your suspicions that your right leg is indeed just a bit stronger than your left.
Pros: DEXA scans are incredibly accurate at measuring body composition. A DEXA scan is quick, dry and painless, involving simply lying on a table for a few minutes. DEXA has surpassed hydrostatic weighing as the gold standard and is being utilized as the criterion measure in clinical research more so than underwater weighing (hydrostatic).
Cons: 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 compared to other methods, which will vary based on location.
Air-Displacement Plethysmography (BOD Pod)
Air-displacement plethysmography is actually very similar to underwater weighing. First, participants sit in a small machine; then, by measuring how much air is displaced 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 for an extended period of time, 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 persons of almost any age, shape and size.
Cons: Like hydrostatic weighing and DEXA scans, air-displacement plethysmography won’t likely be found in your neighborhood gym. While commercial machines might pop up at select high-level training facilities, locating one near you might be difficult. Plus, the cost (between $45 and $60 per reading) might steer you in the other direction.
Regardless of which method you choose, you should wait at least six to eight weeks before re-measuring body fat percentage and use the same method. Find a method that works for you and stick with it. Though bioelectrical impedance and skin calipers tend to be slightly less accurate than more high-tech methods like underwater weighing, they can still be an incredibly useful tool if you just want to track your loss (fat) and gains (muscle). And remember, body composition should be just one metric on the road to health and fitness (alongside others like sleep quality, energy levels and happiness) — not the entire focus of your training.