Round 3: DXA versus Hydro - A Comparison

Cortelli

TL;DR Version: I had both a DXA scan and a Hydrostatic body composition test done today within 2 hours of each other. The results: (1) BF% reported by DXA and Hydro within 0.63% of each other; (2) DXA reports 1.5 lbs extra BF and -3.85 lb LBM (excluding bone marrow!) compared to Hydro; (3) DXA also reports total mass at 174 lbs whereas scale at home, at DXA facility, and at Hydro facility reports 171 – so something is a bit off in DXA or in all three independently maintained scales and in the same manner!; (4) apples-to-apples comparison (hydro to hydro) shows I’ve shed 7 lbs of fat and added 7 lbs of LBM over a six-month period of cutting / maintenance / bulking; and (5) I am happy that I seem to add LBM and fat at a reasonable ratio when bulking.

Full Post: Hello MFPers! Almost exactly six months ago I posted a thread in which I invited commenters to guess my body fat % in advance of a hydrostatic testing I was having done the next day. That thread is here: http://www.myfitnesspal.com/topics/show/1138895-guess-my-body-fat-before-hydrostatic-testing-tommorrow. I followed up with a thread approximately 11 weeks later for a second testing. I was then less interested in direct BF% and more interested in how well I was able to maintain lean body mass, since I was cutting for much of that 11-week interval. That second thread is here: http://www.myfitnesspal.com/topics/show/1193317-round-2-guess-my-bf-total-lbm-before-hydo-test-tuesday.

Following the last test, I was cutting for a few weeks, in maintenance for several weeks, and then bulking for the last 7 weeks in an attempt to add muscle. I *knew* I had successfully added muscle before today’s test, just as I knew that I had “successfully” added back fat, too :ohwell:. The question I was very curious about was: how efficiently can I add muscle, and how much fat is going to join it?

I partially answered that this morning (at least within my capabilities to measure it). Today I was scheduled for my third hydro test through the same service and technician I had used the previous two times. I took the opportunity to have a DXA scan done the same day so I could compare the results. My DXA scan was this morning at 10:15. I then did the hydro at 12:00 noon.

Here are the most interesting aspects of the results, IMHO:

* On an apples-to-apples comparison (hydro 3 months ago versus hydro today, same tech and facility) I have managed to add 6 lbs of LBM (which includes more than muscle of course). I have also “managed” to add 4.9 lbs of fat. Overall, I think a pretty decent ratio during a first-ever bulk.

* On an apples-to-apples comparison from my hydro 6 months ago, I am at virtually the same weight. This is after cutting for 3 or so months, about a month and a half of maintenance in two different stretches, and then formally bulking for 7 weeks. So – roughly no change in absolute weight in the overall scheme from 6 months ago, but: (1) I have added about 7 lbs of LBM; (2) I have shed about 7 lbs of fat; and (3) my BF% has moved from 18.89% to 14.77%.

* I’ve learned a lot about how capable I am at preserving LBM during a deficit and learned a bit about how efficiently I can gain LBM during maintenance and a surplus (I have some newbie gains involved here which are hard to estimate and cloud longer-term expectations).

* The DXA and Hydro were remarkably close in terms of percentages – 15.4% BF from the DXA and 14. 77% from Hydro.

* The LBM totals (in which I was most interested) were more gappy – 141.9 lbs from DXA and 145.75 from Hydro. The DXA does exclude an estimate of bone marrow content which apparently shows up as both LBM and fat in some proportion without the algorithmic removal of it as a separate category.

* The DXA gives a physical map of where fat is stored – it just served to reinforce for me that I store in the trunk and abdomen (though surprisingly less than I would have expected right around the waist given my stubborn pooch and love handles).

* Something is slightly wonky with the DXA scan results. My scale this morning, the scale at the DXA facility, and the scale at the hydro facility all reported right around 171 lbs total weight. The DXA results totaled body mass (based on the compartment readings) at 174 lbs – and the tech assured me that the DXA scan was more accurate than the scale. But that of course means that three separate and separately-maintained scales all reported the same total weight at more or less the same times, and each time were underreporting by 3 lbs. Ok.

* Both the DXA tech and my doctor’s assistant (last physical in Feb / March) are dirty, filthy liars – though really nice, friendly, smart people – when they independently report I have shrunk a half-inch to 5’ 8.5” since my maturity twenty+ years ago.

Anyway, a few pics in keeping with past threads:

Front pic:



Side Pic:



Weight Report from MFP for Last 90 Days:



Hydro Report Summary:



Hydro Report Comparison to Past Reports:



DXA Report Summary:



DXA Report Visuals:



Hope you enjoyed the data!

ETA: fix image tags.