Oh yes, it’s that time again, my annual body composition post. Last year I talked about self acceptance and you got to see some of my heavier photos, those are always fun, eh?

This year I am going to get all data crazy on you. I’ve always wanted to go have one of those DEXA things done. They always use them on The Biggest Loser to tell the people “you are 50% fat” etc etc. I wanted to see what my skeleton looked like and everything I have read said that it’s the Gold Standard in body fat percentages. There is a mobile DEXA unit that comes to my gym once a month so I signed for for a slot, paid my $70 and showed up on time.

I wasn’t nervous…ok, I was a little nervous. Mostly I was excited and really intrigued.

Inside the van was the DEXA machine. It’s a low dose Xray machine as I understand it. You lay there really still and it goes up and down and up and down a ton of times. I would say it takes about 5 minutes.

Then the technician does her work which I’m not sure what that is. Then she printed out three pages for me. I kinda tried to ask her some questions and she said “I’m not really good at explaining the numbers.” So I figured that wasn’t part of the $70, went on my way and figured I had a bit of research to do.

Check me out! How cool is that…it’s me, and I look very skeletal! Very halloween, and I don’t see a lot of fat there…looks pretty lean and good to me. I like the ribs, look at all those ribs, I think I have a barrel chest. Spine looks nice and straight. Look at me, trying to act like I know stuff…

So then come the results. Honestly it’s a lot of numbers that I don’t quite know exactly what they are, but you can see pretty clearly that the DEXA machine (now affectionately nicknamed “Liar”) thinks I have 30.5% body fat. What? Wha? Wh?W? WTF?

The following numbers are quite a hoot to look at as well, check out how fat my left arm is compared to my right. I get that I am right handed and all, but really…I don’t write that much anymore…just a lot of typing really. My right arm is the wonky one in the pool too…maybe it’s too lean and doesn’t float enough?

So of course immediately when I get home I strip down to my birthday suit and make Troy come take pictures of all the scales I have at home and what they think. I used to not even have a scale but now I have a few, and I love them all equally (not really).

First off, my uber-favorite scale, the Withings Scale. This scale is totally awesome because every morning (that I remember) I get on it and it takes my weight, body fat % and BMI. BUT THEN…it automatically uploads my data to the Withings site, the Withings app on my iPhone, AND to Training Peaks, using my wi-fi network at home. Yes, my scale is wi-fi! This seems silly, but it’s actually a really nice feature. So what did Withings have to say?

Humm, Withings thinks 24.6%. So how do scales calculate Body Fat %? Well, they use what is called bioelectrical impedance analysis, which clocks the speed that electricity moves through you and based on the levels of resistance it can determine fat vs muscle. Everything I have read says that DEXA is way more accurate.

I pulled out the Tanita Scale that I have as well. I used to use this all the time and have noticed since getting the Withing that it was usually lower than the Withing. The Tanita thought:

Can you read that? It says 20.9%. It also thinks I gained 0.6 pounds in the 12 seconds it took to go from one scale to the next.

So, what do I think of all this? Other than I paid $70 for a picture of my skeleton? Humm, 30.5%, 24.6%,20.9%. That’s a tough one. I guess what I think from a personal standpoint is that it’s just a number. I know that I am fit, and lean. I wear a size 4, I’m healthy, and I’m not at risk of any serious conditions that I know of.

I think the bigger issue I have is with the recommendations and numbers that have been put out there from the various institutes on health (which in and of themselves are hard to track down):

I found this:

For women, they are considered obese if their body fat percentage is 32% or above, for men this number is 25%. Acceptable levels of body fat include 25-31% for women and 18-25% for men; while athlete’s body fat percentages usually range between 14-20% for women and 6-13% for men.

I also found this:

For women:

  • The recommended amount of body fat is 20 – 21%.
  • The average American woman has approximately 22 – 25% body fat.
  • A woman with more than 30% body fat is considered obese.

Either way, the DEXA is telling me I am either at the upper limit of acceptable, or I am considered obese. I think my favorite is “the average woman is 22-25%”. But the CDC has just revealed that “1 in 3 of US adults is obese”. BMI data was used to make that claim, not Body Fat %. I just think there is a huge disconnect here. HUGE!

Clearly the Body Fat Percentage recommendations are missing the mark when it comes to supposedly accurate DEXA data. I’m not sure what testing system the recommendations are based upon. While I know I am fit and healthy, it does bum me out that the lines of health seem to be so blurry. I’ve heard that BMI is not an accurate indicator of health, I would argue that Body Fat % is not as well. So much research, but so little actual facts.

No 2011 Body Composition blog post would be complete without some photos of my “12 days until Kona Ironman World Championships” body. I’m always a little embarrassed to post these, but I do think they are cool to look back upon and I would urge any of you training for an Ironman to take a few photos in your final days of training.

Not Obese…

I’m really curious on all of your thoughts here! Have you had any body fat testing done? Have you found it to be accurate and/or helpful in determining your proper weight or leanness for a big athletic event? Do you think the information out there is helpful and plentiful? Do you think the DEXA is correct? Do you think the health recommendations are correct based on the DEXA results I saw? I’m so curious what you think!

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health, Ironman, Triathlon

21 Comments

  1. Dear Sonja, I have seen trouble with wrong BCA calibrations on DEXA.
    Pleas ask the people from “DEXA Diagnoses” to show measurments of the Hologic Whole body Phantom.( if they do not have that phantom doubt the values and ask mony back). If these measurments are between tollerance, you know the DEXA (meter) is correct calibrated. Use of the New NHANES BCA ref curves will make a change of about 3-7%, not more.

  2. I have been using DEXA since 1993. The reason for your high body fat % is likely due to the technician using the NHANES database. In using the NHANES database it undertakes a correction process that increases fat mass and decreases muscle mass. I do not use the NHANES database in my practice as I believe its incorrect as I believe you are correct in saying you are definately not 30%. Next time the van comes round get them to re-analyse your old data with the tick box (Utlilities/system configuration/Analyze) uncheck “Enable NHANES BCA”. The get them to do the same with the new scan. This will give you a result that will make sense. All the best, Jarrod.

  3. I’ve never done the DEXA but I have a friend who did a crazy body fat comparison with about 12 different scales, including the one where you get inside the machine that looks like an egg (not sure what it was called). It was FASCINATING to read about, not least of all because of how wildly different the numbers were. I had the caliper test done in high school but don’t think I’ve had it done since. Also, your HEAD has body fat in it? For some reason this thought makes me giggle. I thought it was all brains!

  4. I’ve had the scale with impedance measurements, as well as a skinfold pinch test. Since the skinfold was at my local gym and like $40 each time, I only had it done once or twice, which is like taking your heart rate once a month after breakfast to see if you are getting any fitter. Useless.

    I found I used the impedance scale to track my weight and body fat “%” to maintain my weight when I was training a lot last year. Now, I am scared to go on it. In fact, I left it at Adam’s apartment in Michigan because I have a long road back to being in as good of shape as I was last fall. *sigh* Anyway, the metric I was always taught in college was “if you can see your abs, you are probably under 20%; if you stop having your period, you’re under 14%.” That is math for jock engineers right there.

  5. As others have said, my understanding is that the scales are not accurate in absolute terms (one article found 17% variance!), but they are generally internally consistent. However, I got one a couple months back and notice body fat varying a couple percentage points every day–seems excessive. It also seems, in my experience, to vary a lot depending on whether I am well-hydrated.

  6. That is crazy that all of them had such different numbers! I’m surprised the DEXA tech even let you walk out with a sheet that said you had THIRTY PERCENT body fat. That is just bananas.

    Have you ever tried body fat calipers? I’ve had them in my amazon shopping cart all year. They are just a few bucks and I’ve always been curious how those numbers compare to scales and scans n stuff.

  7. Very interesting! Love what everyone was saying in the comments. First, and most importantly, you are a stellar athlete, and all that should matter is asking yourself, are you still improving? Are you making fitness gains? And are you rocking it out at races? If the answer is yes, then your body comp is right on track for excellence. Secondly, just like a few other people wrote, the Dexa takes into account all fat, not just the unwanted fat. I would love to read a follow up post to this one, and see if you found any charts by Dexa to let you know what your results really mean in “Dexa” terms.

    Personally, I have skin calipers and do skin fold tests 2x a year, and also hop on my scale, and they tend to be pretty similar. But, for me, I always just go by feel, am I performing well, do I feel good about my body, etc.

  8. Wow! That seems so off. I had a Dexascan done last month to check bone density, my insurance covered it but they did not give out a reading of my BF percentage. I guess that part is not included when they are just checking bone density. Now I’m glad they didn’t tell me BF%. I am also questioning how accurate they are. I say a good scale that you use consistently is going to give you more accurate feedback. Plus, the pictures don’t lie. You look great, strong and buff. Maybe ask for a refund?? Did they also give you bone density info or just body fat?

  9. The DEXA is a completely different measurement than the others – notice that an appreciable amount of fat comes from your head? There are lots of fat through the body that are essential to function and not the “under skin” fat that most all of the other tests refer to (nearly all “medical” recommendations are based from skin fold test results and or BMI extrapolation). If you want accurate and precise results, the DEXA is the most likely tool (assuming its kept in proper calibration), but it isn’t really practical or safe for everyday use. Pretty much all other tests other than the water displacement are good for trending over time, but not overly accurate nor precise.
    Cool data points and comparisons though!

  10. Excellent..finally someone with more body fat then me!! Guess I can eat that second bag of Doritos. I’d post pics without my shirt on but am guessing it would kill any traffic to this site.

  11. I don’t ever want a DEXA now! I would be committed to fat camp if you are a 30%! I don’t have much to add here, other than I had a body fat done with calipers when I was in my “weight-training” phase and it seemed pretty accurate. I had it done again at the gym – when I started doing tris and it was higher than 10 years prior (obviously as I my strength training went out the window), I haven’t had it done again. I heard scales weren’t accurate so I figured I wouldn’t buy as I would obsess. You look fantastic – but more importantly you look so healthy and happy – now go get your AG in Kona!! Good luck!

  12. Hmm, body scanning is gold standard? I have always been told/read that underwater weighing was the Gold Standard. The other methods are less accurate (some more than others) but easier to do. Even the underwater weighing is subject to some error – can you really empty your lungs completely for the time it takes to get the measurement? how long can you stay underwater when everything in your body is screaming at you to suck in air?

    Body fat % is a cool number to look at. So is VO2 max. Means nothing when crossing the finish line. It is what is the heart/soul/mind that matters (all other parameters being healthy).

  13. Fascinating. And totally inaccurate, if you ask me.
    I did the underwater fat testing a few years ago.
    http://crosscountrysquared.blogspot.com/2008/11/splash.html

    There’s plenty of margin for error there too. I was in grad school, and the kids doing it looked like he was in the sports science 101 class. Not to mention the water kind of freaked me out. While I probably wasn’t as low as the numbers calculated, I did have amenorrhea at the time and was pretty thin. Who knows.

    I want to do the body pod testing scan. You should make the DEXA people pay for it to compare.

    But regardless of the numbers, you are fit, fly, and ready to kick butt! Good luck!!

  14. That’s interesting about the DEXA. Weird that it said 30%? NO WAY that’s accurate!?! I have a Tanita scale and use it several times/week, but more to assess my hydration levels than anything else. It tells me body fat varies from 16-22% throughout the day based on my hydration level… Clearly the numbers are all just estimates and trends and the only thing that really matters is how you feel and how you perform. :)
    See you next week! Hopefully we can get together to swim early next week? Michelle and I were talking about that… would be cool!

  15. You should march back over there and ask for your $70 back. 30% for you seems absurd. Admittedly, I don’t know much about body fat testing. Only had it done a few times when I was going to a boot-camp type gym for a month. My scale is old and very basic. I get on it every day (or more than once per day to check sweat loss), and that’s about it. You look fab and super fit. All of those other numbers are meaningless.

  16. i think you should ask for your money back…:)

    on a serious note, I agree with CV. you’re fast as heck, so it doesn’t really matter. Lots of people out there talking about body comp and then follow up with a plan to sell you on how to dial in that body comp……

    If performance is lacking or declining, perhaps this is something to take a look at…..if performance is on a steady uptick, your body comp is perfect, and the only reason to know it is curiosity, even then the information could mess with someones head “Am I too fat?” Do I eat too much?” “Shoudl I eat less?”……

    Of course, if they start putting scales at the finish line, we can worry about body fat %….until then, keep doing what you are doing, ’cause it’s working…..;)

  17. I’ve done the hydrostatic weigh and have the tanita. They are always very close. Agree w/ CV though, you are fit and set to rip it in two weeks time!

  18. Take into consideration that the DEXA is a total body scan. That means that the scan takes into account the subcutaneous fat, which is what gets tested with things like skin fold tests, and visceral fat, which surrounds and protects your organs. We have a Tanita scale but I don’t view it, or any scale, accurate for body fat %. It is great for trending increases and decreases in bf%. Body fat calipers and someone who knows how to use them are for more accurate than a scale and water displacement testing is more accurate than calipers. My feeling is that it is not so much an issue with the DEXA, but more that the ranges you found are the recommendations based on skin fold tests which do not take visceral fat into account.

  19. As an aspiring mathematician, I would recommend taking the three averages and then averaging them. Or, better yet, toss them out the window. They’re meaningless.

    Your single best measure is the finish line and your own inner harmony. Beyond that you might consider a hydrostatic test, that is if this really matters to you.

    -CV

  20. Wow, I always thought DEXA was the gold standard for body comp, but…c’mon. That’s RIDICULOUS. You’re obviously NOT over 30% bodyfat. Looking at your pics I’d *guess* 18-19%, but everyone carries fat differently. I look unhealthy below 20% while my boyfriend’s daughter got herself down to 13% for Worlds in Beijing and looked lean but not scary thin.

    I use my Tanita scale. My understanding is that although it’s not super-accurate in and of itself, it shows trends accurately. I still only weigh myself a few times a year.

    My attitude is to go more by how I feel, how my training is going, and finally by how my clothes fit. I usually love numbers, but not in this case.

    Just my thoughts.

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