1 May 2019What Are You Really Made Of?

By relaxing and lying on my back for six minutes and having my body scanned with a DEXA machine, I learned not only about the composition of my total body weight, but I also learned where the fat and lean body tissue were distributed in five different regions of my body. Since I am a right-handed tennis player, recently turned pickleball player, I was curious whether there would be more muscle on my right arm than my left arm.

The DEXA scan (DXA) is the gold standard in terms of telling you accurately about the composition of your weight because it determines what percentage is lean body mass (such as muscles and bones) and what percentage is fat. Especially if you are starting an exercise program, getting a DEXA scan at the beginning of your program, and then after 90 days, is an objective way to measure how your body composition is changing. Since muscle weighs more than fat, the scale may show that your weight is increasing; however, you are actually headed in a healthier direction because you now have a lower percentage of body fat.

Risk of high body fat

You have probably heard of apple-shaped and pear-shaped people. Those who are apple-shaped have more fat distributed around and between organs, such as the kidney, heart, and liver. Having fat in these visceral areas is associated with increased risk of type two diabetes, cardiovascular disease and high blood pressure. Decreasing your body fat through exercise can decrease your risk of those diseases.

History

In the1990's, the gold standard for body composition was called underwater weighing. I remember putting on my swim suit for a physical fitness class, and literally putting my head under the water and blowing out as much air as I could from my lungs to improve the accuracy of the measurements.

DEXA which stands for dual x-ray absorptiometry was originally only used to measure bone mineral density to assess whether a person was at higher risk for a fracture due to weak or brittle bones. However, since the DEXA scan is able to differentiate between fat and muscle tissue as well, today it is considered the gold standard of body composition with an error rate of 1-2%, plus you can stay completely clothed.

Pros

  • Reliable, precise, and fast
  • Only body composition tool that looks at three components not just two
    • Percentage of body fat
    • Percentage of lean mass (muscles)
    • Bone mineral content to test for risk of osteopenia and osteoporosis
  • Regional analysis: breakdown of body fat and lean mass in 5 regions of the body
    • Arms
    • Trunk
    • Belly
    • Hips
    • Legs
  • Tool for athletes to achieve their goals
  • Compares right to left side of body to test for imbalances in muscle development due to injury or usage

If you want to know my DEXA results as a right-handed tennis player, my right arm does have more muscle mass than my left arm.

Cons

  • Cost of DEXA scans can range from $80 - $450. Do an internet search based on your zip code for exact pricing.
  • Not recommended for pregnant women to use any x-ray based test. However, radiation doses are very low in DEXA.

Summary

Weighing yourself on your bathroom scale regularly and noticing how your pants fit are good ways to tell if your weight is headed in the right direction. However, if you ever wondered what percentage of your body is fat and what percentage is muscle and how your body composition is distributed in your body, consider the gold standard of a DEXA scan to find out what you are really made of!

Martha M. Henze, MS, RDN, MPH candidate
Looking forward to graduating in May of 2019 with a master’s degree in public health and focusing on how to help improve our world’s health on a population basis!
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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.

Tags:

Weight Loss/Body composition

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