Measuring Body Fat

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Introduction

Measuring body fat has become a common approach in today’s health and fitness industry. There are benefits to doing this, but there are also some drawbacks. Before you read too much into your personal results, read this NutriWiki article to get a better idea of what those tests actually mean.

Measuring body fat

Summary

  • Every method has limitations in accuracy and precision.
  • Visual estimation or skinfold estimates are the cheapest and most practical, but subject to user error.
  • Advanced methods such as hydrostatic weighing are more accurate, but more expensive.

Discussion

Many people want to get an approximation of their bodyfat percentage to establish a baseline starting point, or evaluate progress over time.

However, there is a fairly large margin of error in most body fat measuring techniques. The only surefire way to get an accurate body fat percentage is via autopsy, by actually weighing all of the fat they take out of your body. Since this requires you to be dead, we don’t recommend it.

With that being said, here is a quick list of each technique, how they’re done, relative cost, and advantages and limitations:

Visual Estimation
  • Measures bodyfat based off a relaxed posture in the mirror. Uses characteristics such as abdominal definition and fat patterning to estimate bodyfat percentage.
  • Inexpensive – Cheapest method of evaluating bodyfat.
  • Can easily be done at home. Only requires a mirror or photographs.
  • Thrown off by bloating, water retention, and subjectivity.
Skinfold
  • Measures bodyfat by pinching subcutaneous fat at several distinct sites. Uses these measurements in a formula to estimate fat mass.
  • Inexpensive – calipers are cheap and easy to find online.
  • Can easily be done at home, either by one’s self or with a second person.
  • User error with the calipers can be significant, and progress is most accurately judged in 3-6 month intervals.
Bio-Electric Impedance (BIA)
  • Sends an electrical current through the body, estimating fat mass based on different electrical resistance of different tissues.
  • Inexpensive – Handheld devices and scales are readily available online.
  • Can be easily done at home. Most BIA devices are very simple to use.
  • Easily thrown off by several factors, including hydration level. Some research suggests it is no more accurate than a simple BMI calculation.
Hydrostatic Weighing
  • Uses water displacement and the principles of buoyancy to estimate fat mass.
  • Expensive – Uses specific instruments not usually found outside special centers.
  • Fairly accurate at estimating group averages in studies.
  • Can have a relatively high error rate for individuals.
Air Displacement Plethysmography (Bod Pod)
  • Uses air displacement to estimate fat mass.
  • Expensive – Uses specific instruments not commonly found outside special centers.
  • Fairly accurate at estimating group averages in studies.
  • Can have a relatively high error rate for individuals. Poor at tracking changes over time.
Dual-energy X-ray Absorptiometry (DEXA)
  • Uses tissue absorption of x-rays to estimate fat mass
  • Expensive – Uses specific instruments not found outside of special centers.
  • Accurate at estimating group averages in studies.
  • Can have a relatively high error rate for individuals. Poor at tracking changes over time.

More Reading

For a more thorough description of the above methods and the literature evaluating them, we recommend this article series by James Krieger, and this one by Lyle McDonald.

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