Discover how to get an accurately test your body composition

The drive to find a way to perfectly measure body composition has been around forever. Over time many tools have been introduced to provide measurements, but many are not as accurate as we would want them to be. Body composition refers to the measure of everything your body is made up of. Mostly we are measuring fat mass and lean muscle mass, but it also includes bone density and body water weight. Scales and handheld instruments were made to quickly give you an idea of these numbers, but they don’t give details and are prone to high user error unless they are used perfectly every single time. There are a few ways to accurately measure body composition though, so let’s dive into the ways with high error, and then how we can get more accurate readings.

Scales and Handhelds

The biggest thing that people do wrong with scales, is not using them at the same time every day. Our body weight fluctuates up to 5 lbs a day based on physical activity, exercise, and hydration. This means that if you weigh yourself at 8am and then 3pm on the same day, your weights could be +/- 5 lbs from each other. While this can still happen from 8am Monday, and 8am Tuesday, by weighing yourself the same time every day you will at least get a more accurate picture of weight changes- even though the actual weights may not be right. Scales also get uncalibrated all the time, and chances are if you are using a digital scale in your home the sensitivity of it changes over time leading to incorrect readings. Sliding scales, like those used in doctors’ offices are a little more accurate but take more time to learn how to use and have much more user error. Overall scales should just be used as a measure of change, not for actual weights. 

BIA, bioelectrical impedance analysis is another scale like measurement that is more accurate than a normal scale, but not as accurate as other forms of measurement. BIA devices send currents through your body and measures how your body reacts. The currents move quicker through muscle than fat because muscles have a higher water content. The movement of the currents is used to predict body composition. While this is more accurate than a scale, food and hydration status greatly affects the readings and there’s a measurement error of 3.8-5%.

There are a few different handheld ways to measure body composition, but like scales, most are not always accurate. The most common one is skinfold calipers. These are plier-looking tool that measures the thickness of the fat underneath your skin. Measurements are taken by pinching the skin with the caliper and the clinician reading the thickness from the caliper. Seven sites are used to measure- chest, abdomen, above the hip, thigh, armpit, below the shoulder blade. A three-site measurement can also be taken and differs for men and women. Men- chest, abdomen, thigh. Women- triceps, above the hip, thigh. While this form of measurement is affordable and requires little equipment, there is a lot of user error as the person performing the test must have knowledge of anatomy and be able to measure in the exact location required. Measurement error with this method can range from 3.5-5% body fat. 

Another common handheld measurement is by simply measuring circumference at different points on the body, normally the neck, waist, and hips. These measurements are then put into an equation along side height and age. While again this method doesn’t require a lot of equipment, there is a lot of user error. Measurement error can range from 2.5-4.5% body fat. It also doesn’t show a good overall picture of body composition. While the areas measured are the usual places people carry body fat, they also are placing that muscle can be carried, and fat can be carried in other places and none in these places.

Electronic /X-Ray Machines

The most accurate ways to measure body composition are a combination of electronic and x-ray methods. DEXA- Dual Energy X-ray Absorptiometry is the most common. With a DEXA scan you lay on your back on a x-ray table and a technician places you in the proper position. Then the machine passes over your body for 10 minutes measuring your body fat percentage, lean mass percentage, and bone density. The machine sends a reading to a connected computer and breaks down the measurements by your arms, legs, and torso for the most accurate readings. Measurement error is usually only around 2.5%. While this is one of the best methods for body composition, DEXAs are expensive and not usually available to the public. If you do have a DEXA available to you, getting measurements up to 3 times a year can provide you with great information about how your body is changing throughout your workout journey.

Bod Pod is another combination machine that provides more accurate readings. Bod Pod, or air displacement plethysmography, uses air displacement to estimate your body fat percentage. You sit in an egg-shaped chamber for 5 minutes while the air pressure around you is adjusted. This is a quick method and pretty accurate, around 2-4% error. But it can be hard for those with claustrophobia, and is very expensive, so it can be hard to find a facility with a Bod Pod.

The standard for body composition measuring is underwater weighing, or hydrostatic weighing. This method estimates your body composition based on its density. You are weighed fully submerged underwater and instructed to exhales as much air as possible from your lungs. Then you’re weighed on land and the amount of air left in your lungs post exhale is measured. All these numbers are entered into equations to determine your bodies density and body fat percentage. While this method is the gold standard and has an error of less than 1.5%, it requires a pool and people willing to spend time underwater with no air. 

The Gold Standard

The most accurate way to measure body composition is called the multi-compartment model. This is a combination of DEXA, BIA, Bod Pod and underwater weighing to measure body mass, body volume, body water, and bone density. Error rates are below 1% and it is considered the gold standard. Combining all these methods provides you with the best picture of body composition from every angle.

Conclusions

So why is all this important? Regardless of your fitness journey to get an accurate representation of what is going on in your body, knowing your body composition is important! For example, if you are working on losing weight and gaining muscle, and only stepping on a scale you might not see any changes. Muscle weighs more than fat, so the scale may show your weight the same, but you may have swapped out some fat for muscle! The only way to tell though, would be through more precise body composition testing like a BIA scan. The measurements can also help predict an injury. If your DEXA scan shows low bone density, you can work with your trainer on more body weight resistance exercises to help increase that density and prevent future injury. To see if any of these more accurate measuring systems are available around you, check out local fitness centers or universities, and talk to your doctor.