What’s the Best Way to Measure Body Composition?
Are you overweight, skinny-fat or just curious about your lean body mass percentage? In physical fitness, body composition is used to describe the percentages of fat, bone, water, and muscle in human bodies. Because muscular tissue takes up less space in our body than fat tissue, our body composition, as well as our weight, determines leanness. Here are 5 common ways to measure – some old and some newer – where you are along with the pros and cons.
Old PARADIGM – Body Mass Index (BMI)
Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It can be mistaken for a marker of health…it’s widely recognized and easy to figure out. It’s not my first choice for measuring body fat and lean mass but still used by many physicians to measure health.
- Enter your weight and height using standard or metric measures.
- An indicator of Body Composition, not a precise measure of body fat.
How reliable is BMI?
BMI is determined by dividing a person’s weight in pounds (lbs) by their height in inches (in), squared and then multiplied by 703.
BMI = weight / [height (in inches)]2 x 703
Some Problems with BMI
You’ll notice this formula doesn’t take age or gender into consideration. It also doesn’t account for the amount of muscle mass an individual may have; many athletes with a large percentage of muscle mass may measure a high BMI even though they do not have excessive amounts of body fat. Women tend to have more body fat than men (reality). Older people tend to carry more body fat than younger people. Athletes have higher BMI because of increased muscularity.
What does a high BMI mean?
A BMI of 18.5 to 24.9 is considered healthy, a BMI of 25 to 29.9 is considered overweight and a BMI of 30 or more is considered obese. If you score a BMI of 25 or above means you are at a much higher risk of suffering from a whole host of diseases including:
- Heart disease
- Cancer (breast, colorectal, endometrial and kidney)
However, this testing method isn’t the best way to know if it’s time to lose weight and can actually be wrong if you’re someone who works out regularly or is older in age.
New Paradigm – Body Composition
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.
Here are the top five methods for measuring body composition along with the pros and cons of each.
Different Types of Body Composition Measurements
1. Skin Caliper
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 of the Skin Caliper Test:
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 of the Skin Caliper Test:
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. Results can vary depending on the number of sites being measured. In my own experience using the 9 site assessment takes in the most information for a more accurate result.
2. Bioelectrical Impedance
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 – probably most common and accessible) 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 of Bioelectrical Impedance:
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 of Bioelectrical Impedance:
Bioelectrical impedance measurements are generally less accurate than other 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.
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 body weight (outside the water) to their body weight while completely submerged. Using these two numbers and the density of the water can accurately nail down the subject’s density. This number is then used to estimate body composition.
Hydrostatic weighing was touted as the gold standard for many years, however, hydrostatic weighing is not able to account for bone density. As a result, hydrostatic tests tend to underestimate body fat in athletic individuals with high bone density and overestimate in older adults who have low bone density. These tests can provide a lot of useful data but many of our clients aren’t sure how to make use of the information.
Pros of Hydrostatic Weighing:
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 of Hydrostatic Weighing:
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 the potential for error) and sit submerged completely underwater, which might be uncomfortable for some individuals.
4. DEXA (Dual-Energy X-Ray Absorptiometry)
Body fat testing is a great way to have an accurate metric for your body composition. There are many ways of getting your body fat tested, but most experts will agree that the DEXA (Dual-Energy X-ray Absorptiometry) scan is the most accurate testing technology available.
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 mechanical 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 of DEXA:
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 of DEXA:
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.
5. 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 of Air-Displacement Plethysmography:
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, make it accommodating for persons of almost any age, shape and size.
Cons of Air-Displacement Plethysmography:
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.
How to Interpret Your Body Composition Results
Most people are rarely excited with their baseline body fat test. Keep in mind that your body fat percentage should be viewed as a metric in the same way that your total cholesterol or liver enzyme values are metrics of your health. It’s a data point we can track over time… not a measure of your self-worth.
This is where you start to take a look at things such as – lifestyle, diet, supplements, medications, aging, and other factors can begin to affect your health.
Most people have a body composition goal, it can also be useful to have this data point tested again to validate whatever training and nutrition strategy you may be using. However, when it comes to aesthetics, I’d argue how you look and feel is probably far more important than a number on a sheet of paper.
That being said, most people want to know more about where they stand and there are various sources for helping you interpret body fat percentages. One of the most commonly referenced charts is from the American Council on Exercise. You’ve probably seen this as a poster or laminated card on a personal trainer’s desk at your local gym.
You’ll notice that women will have a higher body fat percentage at any level compared to men due to biological differences. While the ACE chart is an easy quick reference, it doesn’t account for age and the use of the word “obese” may be a bit extreme in some cases.
Another useful chart is sourced from the research of Dr. Andrew Jackson and M.L. Pollock. Many personal training professionals prefer this chart over the ACE chart as it accounts for both gender differences AND age differences. Simply find your age category in the left-hand column of your respective gender, and then look across to see where you fall in your age group.
1.Body fat charts provided by BodyFatCharts.com
2. Data provided courtesy of AccuFitness, LLC
Body fat percentage is only one metric that people tend to fixate on when setting their fitness goals. It also provides another very important number: lean body mass (LBM). Your LBM is simply your body fat subtracted from your total body weight. LBM includes organs, bones, muscle, and everything else in your body besides body fat. Typically, changes in LBM are primarily from increases or decreases in muscle mass. Changes in bone density can affect your LBM as well, however, a DEXA scan will be able to differentiate between the two. Usually, this is listed as Bone Mineral Content (BMC) on a DEXA report. It’s important to note that when viewing a DEXA report, LBM is calculated by adding the “Lean Tissue” and “BMC” measurements together. A hydrostatic test will give you LBM and body fat only.
If your goal is to get leaner, you need to decrease your body fat percentage while maintaining (or increasing) your LBM. It’s important to keep an eye on both numbers as you work towards your goal. Your LBM is also very useful for helping us calculate your daily nutritional requirements.
Things to Consider when Looking at Body Composition Numbers
Body Fat vs Body Muscle
You may have heard the phrase, “Muscle weighs more than fat.” But how true is that? Well, common sense tells us a pound of muscle and a pound of fat have to weigh the same; however, they do differ when it comes to density. This means if you look at five pounds of muscle and five pounds of fat side by side on a table, the fat will take up more volume, or space, than the muscle.
The same holds true with your body; you may look noticeably leaner due to fat loss, but when you add in muscle gain, the weight on the scale could be up five or maybe even ten pounds more than it was before. Most scales can’t tell the difference between what’s fat and what’s muscle, so that added weight could be muscle that you’ve worked so hard to obtain!
If you look and feel leaner but your weight is up on the scale, then a body fat percentage testing method may be a better choice for those who like to set milestone numbers for body composition goals.
You Are Not Defined by a Number
You’ve probably seen this phrase posted on someone’s Facebook or Instagram at some point, as it has become a popular motivational phrase in the fitness community. That doesn’t mean it’s not true, however.
Ask yourselves – at the end of the day, which is more important: how you look, feel and perform, or what the cold-hearted scale tells you whenever you step on it? If you look and feel like a lean, mean beastmode machine, it shouldn’t really matter if you’ve gained a few pounds in the process. If you’re healthy and you look good, don’t put too much stock in what the scale is telling you.
Obsession Can be a Slippery Slope
It’s no surprise that eating disorders and obsession about our weight have become commonplace in America; almost 30 million Americans (of all ages and genders) suffer from some type of eating disorder .
Now, I’m not saying that everyone who weighs themselves is obsessed or will become obsessed at some point; I can only speak from personal experience. There was a time when I wrote down and recorded every single thing that I ate and drank; I also would weigh myself 2-3 times a day. I did both of these things every single day for months at a time; and when I decided I needed a mental break from all of that dedication, I found it to be actually quite hard for me to stop, as weighing myself became a habit – an obsession – that was very hard to break.
For those of you who weigh themselves on a regular basis, I challenge you to hide your scale away and not weigh yourself for seven days. If it’s too difficult of a challenge and you find yourself unable to break the habit, it may be time to set some new goals and create some new habits that will help you towards your goals versus stressing you out about them.
SUGGESTION – weighing yourself only once a week, same time, same place – consistency. Stick to one source.
Bonus Reason just for Females: Hormones
Yes, this reason needs just one word to sum it up. Hormones play a big role in wreaking havoc on the scale for women, even causing their weight to fluctuate from day to day, depending on your time of the month. You may not feel bloated, but you could be retaining fluids. Studies have shown that women hit a peak day of fluid retention at the start of their menstrual cycle, with some women retaining fluids the days leading up the cycle. So if it’s close to your time of the month, don’t put too much stock on what you see on the scale
Remember What’s Important
We all want to be healthy, look great and perform our best in life, both inside and outside of the gym. Obsessing about the weight on a scale can actually get in the way of your body composition goals. If your current goal is weight loss and you constantly find yourself in the scenario described at the beginning of this blog, it may be time for some new goals that don’t revolve around the scale, such as dropping a pants/dress size or using a tape measure instead of the scale to keep track of your growing biceps.
And remember, at the end of the day, your weight is just a number showing the “amount of downward force gravity is exerting upon you” and nothing more.
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