How to accurately measure your body fat percentage Part 1
So there I was. I stood in front of the mirror and was slightly confused. What was my body fat percentage? Bodybuilders compete with a body fat percentage of 4 to 5% and look like living anatomy diagrams, so I thought I should be around 7%.
But not according to my trusty Caliper test with multiple measuring points - this one said 11%.
I was confused by this measurement as I couldn't squeeze more than a little skin anywhere on my body, but I should still be carrying around almost 10 kilos of fat.
To put this into perspective, one kilo of fat is equivalent to 4 packets of butter. Where exactly could I have hidden those 40 packets? And considering the effort it took to get as slim as I was, the question arose as to whether it wasn't completely impossible to achieve a body fat percentage of 7% naturally.
Well, I started looking for answers and in this article I will share with you everything I have learned. By the end, you'll know what the term body fat percentage really means, you'll know the pros and cons of the most popular methods of measuring body fat percentage, you'll know how to get an accurate estimate of your body fat percentage, and much more.
What is your body fat percentage?
Many people confuse the terms "body composition", "BMI" and "body fat percentage", but these terms describe different concepts.
The term body composition refers to an analysis of what your body is made up of - skeletal muscle, fat, bones, organs, blood, water, etc.
BMI is short for "Body Mass Index" and is a numerical expression of the relationship between your height and weight.
And the definition of body fat percentage is clear from the name - it is simply the percentage of your weight that is made up of fat.
So when you measure your body fat percentage, you are determining how much of your weight is fat. Let's look at an example to make this clearer:
Let's say a person weighs 75 kilos and 7.5 of those kilos are made up of fat. This person's body fat percentage would be 7.5 divided by 75, which is 10% expressed as a percentage.
This percentage changes when this person gains or loses fat and it also changes when this person gains or loses muscle.
For example, if that person follows an appropriate diet and exercise program and gains 10 kilos, of which 2.5 kilos are fat, then that person will weigh 85 kilos with 10 kilos of fat.
This would visibly change the visual appearance, while the body fat percentage would remain almost the same, which would now be 10 divided by 85 or about 11%.
Let's say this person then stops training with weights for 10 years and loses 5 kilos of muscle but no fat. Again, this would make a big change in the mirror, but his body fat percentage would still be more or less the same - about 12% (10 divided by 80)
The bottom line is that your body fat percentage is a sort of "moving target" that changes based on what happens to your body and body composition over time.
Why is body fat percentage more meaningful than BMI?
As we have already seen, BMI is the abbreviation for "Body Mass Index" and represents the relationship between a person's height and weight. To calculate the BMI, divide your weight in kilos by your height in meters squared.
Let's take my values from the situation above as an example: 83 kilos in weight with a height of 1.85 meters. First, let's take the height squared
1,85 x 1,85 = 3,4225
Then we divide the weight by the square of the height to obtain the BMI:
83 / 3.4225 = 24.25 (BMI)
According to the BMI table, different BMI values correlate with different weight categories:
- Underweight = BMI below 18.5
- Normal weight = BMI between 18.5 and 24.9
- Overweight = BMI between 25 and 29,
- Obesity = BMI from 30 or above
So according to this BMI measurement, I was on the cusp of being overweight... while at the same time having visible veins on my abs - and therein lies the problem with BMI: while it can be useful for analyzing large populations, it's not very helpful as a tool for estimating individual fitness - especially for people with above average amounts of muscle mass.
If you're trying to estimate your individual fitness, you're much better off using your body fat percentage.
How can you accurately measure your body fat percentage?
Measuring body fat percentage seems quite simple at first glance, but it can also be very confusing - and this is true regardless of the method you use, as unfortunately all of them have some margin for error and can give wildly different results.
For example, the caliper test with several measuring points gave me a value of 11% but an electrical measurement gave 8% and a caliper with only one measuring point gave a value of 6%.
What exactly does this mean? Are body fat measurements nothing more than a shot in the dark? Is there any way to determine your true body fat percentage?
Let's find out.
Body fat scales and handpieces for measuring body fat percentage
The easiest way to measure your body fat percentage is to use a body fat scale or handheld impedance meter. These measurements are quick and easy, but what you gain in convenience you lose in accuracy.
These devices use a method called bioelectrical impedance analysis (BIA), which measures the body's resistance to an electric current. The science is simple:
Muscle tissue conducts electrical current very well because it is more than 70% water, while fat is a poor conductor because it contains less water.
Theoretically, the fatter a body is, the higher the electrical resistance should be.
Sounds plausible, doesn't it? Sure, it sounds quite plausible, but the bioelectrical impedance measurement has some serious flaws.
1. the electric current takes the path of least resistance.
This means that the current will bypass the fat stores in favor of the tissue with a lower resistance. As you can imagine, this will distort the results.
2. most body fat scales and handpieces only use two electrodes.
This is a problem because the current can skip whole areas of the body (1). For example, a foot to foot measurement can bypass the entire torso and a hand to hand measurement can ignore the lower body. This naturally leads to inaccurate values.
3. readings can vary dramatically depending on the condition of the body.
The accuracy of bioelectrical impedance measurements is also undermined by the fact that the measured values are influenced by different physical factors.
For example, a measurement in a dehydrated state may result in abnormally high body fat values (2) and a test after a meal may result in abnormally low values (3). A test after a meal reduced the measured body fat percentage in one study by 4.2 percentage points (4) and a measurement after exercise can also provide inaccurate values (5).
4 The equations used to determine body fat percentage are often fundamentally flawed.
I know I'm riding a dead horse here, but there is another major drawback that you should know about. Turning an electrical impedance measurement into a body fat percentage requires mathematical calculations and these calculations often spit out incorrect values.
The manufacturers of these devices have taken several steps to create these formulas:
- They accurately determined the body fat values of a large control group of people.
- They then measured the body fat percentage of the same subjects using a bioimpedance meter from this company.
- Finally, the measurements were compared and an equation was developed to determine body fat percentage from the bioimpedance measurement based on variables such as height, weight, gender, etc. This may be a good theory.
This may be a good idea in theory, but the problem lies in step 1 - the method used to determine the "control values" - for the following reason:
Most of the methods used to determine this calibration data are themselves flawed.
A lot of companies use hydrostatic weighing, for example, and studies have found that this measurement can deviate from the actual value by up to 6 percentage points, depending on factors such as ethnicity, body weight and level of hydration.
And these errors are absolute - not relative. (A person with a body fat percentage of 10% can easily be diagnosed with a value of 16% when measured in a hydrostatic tank.
And what do you get when you use inherently falsified control methods to calibrate the inherently incorrect readings of bioimpedance devices?
A very poor method of measuring body fat percentage.
The bottom line on bioelectrical impedance measurement
As stated earlier, bioelectrical impedance measurement devices available to consumers are so inaccurate and prone to error that scientists have said that these devices are simply not a viable way to estimate body fat percentage (6).
Even the better commercial devices cannot guarantee accurate values. And since these inaccuracies are inconsistent on top of everything else, you can't even use bioelectrical impedance measurement devices to determine a trend in your body fat change over time.
(If they were at least consistently inaccurate, you wouldn't know your actual body fat percentage, but at least you'd have a good idea of whether you're losing fat or muscle).
Body fat calipers and skinfold measurements
Skinfold measurements work as follows:
You use a tool called a caliper to measure the thickness of your skin folds on different parts of your body. You then add up these measurements and apply a formula developed to estimate your body fat percentage.
It should come as no surprise that this method also has some weaknesses and disadvantages.
1. the result is very prone to user error.
Squeeze too much skin and you will get a reading that is higher than your actual body fat percentage. Squeeze too little skin and you will get a measurement that is too low.
2. even if you take a perfect skinfold measurement, bad formulas can still falsify the result (7).
One study found that the results of skinfold measurements can deviate up to 15 percentage points from the actual body fat percentage, with the average deviation being 6 percentage points (8).
Two other studies on skinfold measurement (one of which was conducted with bodybuilders) found error rates of 3 to 5 percentage points (9, 10)
However, despite these weaknesses, calipers and skinfold measurements can be a useful way to determine changes in body composition over time - more on this shortly.
Dual-Energy X-Ray Absorptiometry (DEXA)
DEXA is definitely the most high-tech option on this list.
For this method, a full-body X-ray is taken, which is then used to calculate body fat percentage (radioactive rays are absorbed differently by fat and non-fat tissue, making it possible to measure both types of tissue separately.
DEXA is often referred to as the "gold standard" in body fat measurement, but scientific research shows that this method is just as unreliable as the other methods on this list (10).
One study found that DEXA measurements can be off by 10 percentage points (11). Two other studies found error rates as high as 4 percentage points (9, 12).
This helps explain why many bodybuilders were confused by DEXA scans that were in the 6 to 10% range, even though they were performed in their absolute leanest state.
Here are the reasons DEXA isn't as great as many people think:
- The accuracy of the machines is affected by a whole host of different variables including gender, height, body fat percentage, diseases, and hydration status (13, 14).
- Different machines use different algorithms to convert the raw data into body fat percentage and some algorithms are better than others.
- The type of X-ray affects the accuracy of the test (15).
- Different machines produce different results - even two machines from the same manufacturer.
Unfortunately, there is no way to know if the results of a DEXA scan are truly accurate.
Body Pod
The science behind the Body Pod is similar to that of hydrostatic weighing. You sit in a sealed chamber and sensors measure the amount of air displaced by your body.
The measurement results are used as starting values for different formulas that are used to calculate your body fat percentage.
Now, we already know that hydrostatic weighing often leads to incorrect results and it seems that Body Pod measurements are even less accurate (16).
The values can be affected by many different factors including body temperature (17), facial hair (18), humidity (19) and even the tightness of clothing (20). Taking all these variables into account, it is not surprising that scientific studies have concluded that the Body Pod has a fairly high error rate.
In one study, the test was off by up to 15 percentage points (16). In other studies, the error rate was up to 5 or 6 percentage points (21).
I can confirm the inaccuracy of the Body Pod. I have worked with thousands of people over the years and have met dozens of people who have been upset by insane Body Pod readings (men with visible abs who had Body Pod readings of over 20% body fat).
In the second part of this article series, we will look at other methods of determining body fat percentage and present a very accurate strategy that will help you to monitor whether your weight loss efforts are going in the right direction.
https://www.muscleforlife.com/how-to-measure-body-fat-percentage/
By Michael Matthews