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How Accurate Are Fat Calipers? (And What Is The Error Measurement Range?

Fat calipers are notorious for being inaccurate when it comes to measuring body fat. Compared to hydrostatic weighing or underwater weighing which are arguably the best options when it comes to accuracy, fat calipers promise convenience and affordability.

Today I would like to focus on:

a) Factors affecting the accuracy of Fat Caliper results
b) Tips that you can practice to improve your accuracy the next time you’re measuring
c) Level of Inaccuracy of Fat Calipers

1. Factors affecting the accuracy of Fat Caliper results

Nothing beats fat calipers when it comes to convenience. From their relative affordability to being portable, the chances of you going wrong with calipers are very slim.

This convenience, however, comes at a cost that I think is important to highlight. If you are planning to use calipers as your tool of choice then here are a few factors for you to consider:

i. The accuracy of your results is directly related to how accurately you locate skinfold sites

There is more than one way of performing a caliper test, and this in itself causes problems since people choose the one that suits them the most.

The most accurate test however is the Jackson and Pollock equation, which involves taking measurements from 7 sites of your body:

  • Thigh
  • Suprailiac
  • Abdominal
  • Subscapular
  • Axilla
  • Triceps
  • Chest

Once these sites are located, ensure you properly mark them. Specialists encourage using a big X which will give you adequate guidance on where to place the caliper jaws.

As simple as it is, this rule must be followed to the latter to ensure maximum accuracy. I know it seems to just eyeball the whole thing but resist the temptation and pick up a tape measure.

Just in case you’re wondering, the abdominal site is 2 cm to the right of the navel, can you eyeball that? If you can, then well done.

ii. Technique is key

Now that you have the first step down, the next hurdle will be how you handle the calipers. Remember the X marking on the 7 sites? This is where they come in handy.

The Center for Disease Control’s guidelines on caliper rules provides the guidelines to be followed when locating the skinfold sites and how exactly the caliper jaws are to be placed on each skinfold. Please go through them if you can as those will improve your measuring life significantly.

Here are examples of some of the guidelines:

  • When taking measurements of the subscapular (Shoulder blade) place one jaw directly on the X and another jaw on an unmarked portion of skin.
  • On the tricep, however, place the two jaws of the caliper on either side of the X.
  • It is advisable to take reading about pinching on the skinfold and wait for approximately 3 seconds.

All these small procedures are absolute if you want accurate results.

iii. Caliper results take into account empirical estimations like age

The Jackson and Pollock equation which is used to calculate body density is part of a 2 equation step that is meant to turn the skinfold measurements into a fat percentage.

The equation accounts for age as one of the variants to adjust and increase its accuracy, making it look like this:

Body Density = 1.112 – (0.00043499 x sum of skinfolds) + (0.00000055 x square of the sum of skinfold sites) – (0.00028826 x age)

By accounting for age, however, the equation assumes the effects that age has on body density consequently misrepresenting people that fall outside the normal range for their age.

iv. Caliper equations carry assumptions about Body Fat distribution in the body

Equations such as the Jackson and Pollock Equation rely on math to turn your measurements of skinfolds into meaningful body fat data.

For this to be possible though we need to assume completely the type of fat that we are measuring. This makes this method particularly inefficient for overweight people who might want to know more about their visceral fat than their subcutaneous fat.

2. Tips that you can practice to improve your accuracy the next time you’re measuring

Now that we know what to look out for, here are a few tips to help you the next time you find yourself with a pair of calipers:

i. If possible have the test carried out by a professional
ii. Skin should be dry and rid of sweat or other fluids such as lotion
iii. Do not eyeball the sites, ensure you identify them correctly and write them down. Especially if you’re planning to keep on measuring yourself.
iv. Ensure your measurements are taken at the same time of the day and under the same conditions to maintain consistency
v. Use quality calipers. Quality calipers exert constant pressure enabling them to stay accurate when placed on the skin.

3. Level of Inaccuracy of Fat Calipers

Fat caliper results will vary widely if not done properly, mainly because of the human error element that accompanies it.

Overall though they will provide reasonable results that are up to 4% of other accurate methods like underwater weighing or a DEXA scan.

So how accurate are fat calipers? (And what is the error measurement range?)

Fat calipers are going to be fairly accurate if these four factors are carefully considered:

i. The accuracy of your results is directly related to how accurately you locate skinfold sites
ii. Technique is key
iii. Caliper results take into account empirical estimations like age
iv. Caliper equations carry assumptions about Body Fat distribution in the body

If these are followed to the latter then the 4% accuracy levels won’t be something to worry about.