Your weight tells you little about your body fat content. The number the scale spits back at you is a measure of the weight of all the tissues in your body, including lean body mass, and fluid. The most accurate ways to determine your body fat percentage is to visit a medical facility that does these measurements. Depending on the method they use, it can be expensive. A low-tech way that you can use at home is to measure skin folds using an inexpensive pair of calipers. The question is how accurate is this method? Are skin-fold measurements a reliable measure of body fat percentage?
You’ve probably seen calibrated calipers that you use to do a pinch test at various points on your body. These calipers are designed to measure the diameter of subcutaneous fat you have underneath your skin. Once you’ve done the measurements, you add them up and use an equation to calculate your body fat percentage.
Accurate Skin-Fold Measurements Are Technique Dependent
To measure skinfold diameter, you grasp a fold of skin between your index finger and thumb and lift it away from your body. You then grasp the skin with the calipers about 1 centimeter below and at right angles to the pinch. Be sure to grab only fat, not muscle or fascia. For the technique to be accurate, you must use fixed pressure at each site. Unless you grab each area with uniform pressure, the results will be inaccurate – and it takes practice to learn to keep the pressure consistent. You need to measure using the calipers at three or more sites. Some sources recommend measuring at up to seven sites but three sites will work.
In women, the sites are:
· The thigh – Place the calipers midway between the hip and the knee. Grab the skin so that you form a vertical fold.
· Suprailiac area – Place the calipers 1 centimeter above the anterior superior iliac crest, the top of the hip bone. Use a diagonal fold
· Triceps region – Place the calipers midway between the shoulder and the elbow on the back of the arm. Use a vertical fold.
To get the most accurate measurements, take two readings at each site. If the values vary by more than 1 mm, take a third measurement and average the three. When you take more than one measurement, don’t do them consecutively. Measure all three sites in sequence and then go back and remeasure a second time. Doing this gives the skin time to return to its normal shape. Don’t switch between sides when you measure – take the measurements only from the right side of the body.
For the greatest accuracy, be sure the calipers you’re using are properly calibrated. This ensures they have the proper jaw tension.
How Accurate Are Skin-Fold Measurements Using Calipers?
One of the biggest problems with using calipers is they’re very much operator dependent. If you ask a few different people to take measurements, they’ll likely each come up with values that are slightly different. This makes them a less than an optimal tool for calculating absolute body fat percentage. Plus, factors like hydration status can alter the readings slightly as well. What they’re better for is monitoring for CHANGES in body fat over time.
After measuring the skin fold at each site, record the values in a notebook and keep them for future reference. When you remeasure in the future, compare the values to the previous values. You can also add up the values at each site and get an estimate of body fat percentage using a table designed to give you this information, keeping in mind the limitations of the method. You can also find 3-skinfold calculators online to plug the values into.
Because the results are user dependent, the same person should do the measurements each time. If the person measuring has a “heavy hand” and pinches too aggressively, your body fat will be falsely elevated. If they pinch too little, it will underestimate it.
Don’t Place Too Much Stock in Skin-Fold Measurements
Here’s where skin-fold measurements using calipers really fall short. This method only measures subcutaneous fat, the fat the lies just underneath your skin. What it can’t measure is visceral fat, a deep type of abdominal fat strongly linked with health problems, like type 2 diabetes and cardiovascular disease. In terms of health risk, this is the most important type of fat. You might have a low body fat percentage as measured with calipers, yet be at high risk for health problems because you have a large amount of visceral fat that can’t be measured with calipers.
Some skin-fold formulas and calculators include age in the equation to compensate for this, as visceral fat tends to increase with age. If you’re older and use one of these formulas and happen to NOT have a lot of visceral fat, the caliper method will overestimate your body fat percentage.
Are There Better Methods for Measuring Body Fat Percentage?
If you don’t mind paying more money and going high tech, you could have your body fat percentage measured via an x-ray scan called a DEXA. Health practitioners call the DEXA scan the “gold standard” for measuring body fat percentage but it, too, isn’t 100% accurate. Studies show that it can under or overestimate body fat by up to 10 percentage points and different machines can yield different results.
Then, there’s the Bod Pod. You sit in a chamber closed off from the outside. The Pod is a substitute for hydrostatic weighing, determining how much water your body displaces. Like the DEXA, it can deliver varying readings, partially because factors like hydration and body temperature can influence the results.
Finally, there’s another at-home option for monitoring body fat percentage – bioelectrical impedance scales. Like skin-fold measurements, bioelectrical impedance readings can be thrown off by a number of factors, particularly hydration status. If you measure first thing in the morning, right after urinating, and before drinking fluid and do it consistently, it can be helpful for following changes in body fat percentage.
The Bottom Line
Nothing beats skin-fold calipers in terms of cost, yet they suffer from being so dependent on user technique. However, other methods of measuring body fat percentage aren’t entirely accurate either. If you go the caliper route, buy a quality pair, keep them calibrated, learn the proper technique, and use it to monitor for changes in your body fat percentage over time.
References:
Top End Sports. “Skinfold Caliper Calibration”
Arch Dis Child. 2006 Jul; 91(7): 612–617. doi: 10.1136/adc.2005.085522.
Med Sci Sports Exerc. 2004 Jun;36(6):1070-7.
Muscle for Life. “How to Accurately Measure Your Body Fat Percentage”
Am J Clin Nutr. 1999 Jul;70(1):5-12.
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