Getting dunked and finding some surprising results...

As you may know, the very first step I laid out for myself to become badass was to get to 8% body fat. For a 33 year old, that's a respectable number. Heck, it's respectable at almost any age.

Heretofore, I had been using bioelectric impedance devices, either a handheld Omron or more recently, my nifty Withings scale which automatically sends the data via wifi to my phone. The pro of this method of body fat testing is that it's easy and cheap. The con is that accuracy is suspect, and the test is highly sensitive to differing levels of hydration. However, by always measuring at the same time every morning, in the exact same way, I was pretty sure that the data I accumulated gave a relatively accurate trend line.


Today was the day to find out where I truly stand on the body fat progression - my very first encounter with hydrostatic testing, long considered to be the gold standard. I had the pleasure of working with Aeron Dietz from Fitness Wave Norcal who made the process super easy. But before getting into that, I thought some of you might want to know how this test actually works. Surprisingly, it's based on Archimedes Principle, discovered by Archimedes of Syracuse back around 200 BC. The principle states that the buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid displaced.

Ok, but how does that get converted into body fat %? Well, lean mass has a different density than fat mass. In fact, lean mass is more dense than water, and fat mass is less dense. Pound for pound, lean mass and fat both have a constant mass and both displace a specific amount of water. Using this, one can calculate the body fat percentage.

So thanks for indulging me in a little history. Back to the process. First, you weigh in on the scale and get a frame estimation with an ankle circumference measurement. I forgot to ask Aeron how the ankle circumference factored in, but I'll be sure to ask next time. Then you strip down to swimwear, get into a warm tub, and lie across a submerged metal rack in a stretched out position. And the most surreal part is this. In a highly, counterintuitive fashion, you actually try to breathe out all of the air you have in your lungs while submersing yourself in the water. It's actually kind of fun to try, and a bit weird at first. After doing this 3 times and a few minutes later, the computer spit out the results.

I asked Aeron if he could guess my body fat, as he's seen this many times before. His guess was that I had less body fat than my Withings scale was telling me, because he was certain I had less than 15 lbs of fat, based on the definition of abs and upper back. My latest scale reading said 11.7% this morning, so I figured, I could be in the 10% range.

Turns out the test put me at 9.3%!! It's not 8%, but it's a fair bit closer than I thought. As I processed this new information, I quickly came to a decision of how I was going to use it. My original goal was 8%, and that was based on reducing my body fat by half. That, I decided, should still hold. So if my body fat was 15.8% according to my scale on June 1st, then I will continue working towards half of that. Assuming a constant difference between the scale and hydrostatic testing, that would actually put me in the 5-6% range. Let the games continue...