2 April 2019Body Fat Testing Using the BOD POD

Our body weight and BMI do not tell us the full story about our health. Do we have enough muscle and/or too much fat? Too much body fat near our organs means a higher risk for heart attack, diabetes, high blood pressure, and other health problems. But how do we know if we have too much fat? That is where body composition analysis comes into play.

Air Displacement Plethysmography

Most folks know this as the BOD POD test. The nice thing about this test is that there is no radiation exposure, water dunking, or skin pinching.

How does it work?

BOD POD measures body composition using whole-body densitometry. A person's body weight and volume is measured to find the body density. With an accurate body density, the % fat and % fat-free mass (e.g. muscle, water, bone, and organs) can be estimated. The physics behind the measurements is related to Archimedes' Principle regarding the physical law of buoyancy, but instead of water displacement, the calculation uses air displacement. If you would like to learn more, visit Cosmed's BOD POD.

How accurate are the results?

According to the clinic director of the health and wellness center I visited, the BOD POD has "a margin of error of 1% - 2.7%." The BOD POD is reported to be very accurate compared to underwater weighing. Underwater weighing was once considered to be the gold standard for body fat measurement until dual-energy X-ray absorptiometry (DXA/DEXA) became widely available (now that is the gold standard).

I did find one study (Air Displacement Plethysmography versus Dual-Energy X-Ray Absorptiometry in Underweight, Normal-Weight, and Overweight/Obese Individuals) that concerned me - the authors found that the BOD POD didn't measure accurately when adults were far below or above a healthy BMI. Body fat was measured about 13% too high for the underweight and about 8% too low for those with obesity. It remains to be seen if further studies confirm this problem - I haven't seen this error reported elsewhere.

What are optimal testing conditions?

Person has to be nearly naked - they are instructed to wear a tight fitting bathing suit (or 2-piece suit) and a bathing cap. All jewelry, metal, bra pads, etc. are removed before the test. Also, no exercise, eating and drinking of any liquids within 2 hours of the test.

Pros:

  • Cost. For the accuracy of the measurement, I think this method is reasonably priced between $50-$80 per test, depending on location and facility. For example, in the same facility I visited, a DXA for body composition would be $139, nearly double the cost of the BOD POD.
  • Fast. The test itself takes about 5 minutes. The entire visit was 20 minutes if I include getting basic questions answered about the BOD POD.
  • Somewhat accessible. This method is becoming more common in weight loss clinics and specialty gyms, so if you live in a city, you are likely to find it by searching "BOD POD" in your area.
  • Accurate. If you want accuracy without expense or physical discomfort or radiation exposure, this method is great.
  • All ages. Test can be performed accurately from age 2 years onwards.

Cons:

  • Nearly naked. If you are very self-conscious about your body and how it looks without clothes on, then this is not a good method for you.
  • Claustrophobic? If you panic or get very anxious in close spaces, this method might not be a great choice. However, while seated inside the capsule, you do face a clear plastic window so at least you can see out.
  • Ear popping. There is a small amount of ear popping during the test. I think it would not be comfortable if you were sick with a sinus or ear infection.
  • No detail about where fat is located. My biggest complaint about this method is that I don't know where my body fat is distributed. Unlike the DXA test which shows you where your fat is located, this test only gives you total % fat mass and % fat-free mass. If my % fat mass is on the high end, is it because I have a very curvy woman's figure (not a health risk) or is it because I have too much fat near my organs (health risk), or some combination of both?

Conclusion

BOD POD is an easy, somewhat affordable way to get a highly accurate body composition measurement. If you need more detailed information about where your fat is located in terms of risk for disease, then I would invest in the DXA test instead of the BOD POD. Also, if you are very underweight or have a lot of excess weight, then I would opt for the DXA instead of the BOD POD.

Stay tuned for more blog posts on body composition methods at MyNetDiary! Here are some related posts on this topic:

Katherine Isacks, MPS, RD, CDE
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Disclaimer: The information provided here does not constitute medical advice. If you are seeking medical advice, please visit your healthcare provider or medical professional.

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Weight Loss/Body composition

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