DEXA Bodyfat Scans


Many people become devastated when they get the result of their DEXA scan as it is far higher than they anticipate.
People tend to defer to the ‘experts’ even when common sense says something is wrong. Just because an answer comes from a computer does not make it correct. For many decades we used things like flotation displacement tanks and skinfold calipers to measure bodyfat and with those we came up with charts like this:

I can guarantee you that if your DEXA scan reports 30% that you look NOTHING like the 30% photo here. Here is what is my guess at what is going on. I would be willing to bet that in a decade somebody is going to say:

“Oops, sorry, bug in the DEXA software – we have been drastically over-stating bodyfat”

The way a DEXA scan calculates bodyfat is that the machine has to categorize every bit of your body into pigeonholes: muscle, fat, bone, organs, connective tissue, etc. Either the sensors are not capable of accurate determination OR the software is incorrectly interpreting the data. We have a saying in software engineering – garbage in, garbage out. If the data from the sensors is not capable of accurately differentiating between various types of tissue then there is nothing the software can do to compensate.

With bodyfat, what its not important at all what artifical number you assign to it – its just a number! What is important with bodyfat is:

  1. Is the current bodyfat optimal for performance? This will depend on what your sport is. Linebackers and sumo wrestlers will perform better at a much higher bodyfat than marathon runners or gymnasts. A DEXA scan tells you nothing, your training, event results, and coach can tell you what is optimal.
  2. Is the current bodyfat optimal for aesthetics? A DEXA scan is useless here, a mirror is the ultimate and definitive authority.
  3. Is your bodyfat increasing or decreasing? A DEXA scan is useless here because you need daily or at least weekly feedback on this and daily DEXA scans would put you at risk of cancer from radiation as well as cost a fortune. The best way to know if your bodyfat is increasing or decreasing happens to be the simplest and the cheapest also – use a measuring tape on your waist!
  4. Is the current bodyfat optimal for health? There is zero data linking DEXA bodyfat measurement to any health outcomes. There is a lot of research that shows optimal longevity and health using the traditional bodyfat measurements.