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DEXA vs Calipers for Body Fat Estimation

Since the beginning of my career I’ve emphasized the importance of paying attention to body composition over body weight alone.  In most of my books I tend to base diet set up on body fat percentage as well as that determines a lot about someone’s physiology.  But my numbers are generally based on older methods, primarily caliper measurement.  And in that DEXA is becoming more common, I want to look at DEXA vs calipers for body composition measurement.

DEXA vs Calipers, etc.

One of the more recent approaches to measuring body composition is DEXA (Dual-Energy X-ray Absorbitometry) which does a full-body scan and can measure things like bone density (critical for women) and other tissues.  And it gives what is proposed to be a more accurate estimate of BF% than older methods.  It can even do something where it gives you one value for upper body and one for lower body. I suppose folks could use this to look at regional changes in BF% but I think whole body BF% is more valuable.

And here’s where it gets a little bit weird.  DEXA seems to give systematically different measurements than other older methods.  And it seems that they are usually higher.  Case in point, a number of contest lean bodybuilders (who calipers or visual estimates might put around 4%, the lower limit for males) have been DEXA’d at like 9% or thereabouts.

And what I’m seeing online is that someone will ask for a visual estimate, they will be very lean and maybe estimated at 8% and someone will comment “Yeah, such and such contest lean bodybuilder was estimated at 9% so no way are you 8%, lol.”   Lol indeed.

But here’s the thing, you can’t compare apples and oranges like this (well you can but why would you).   DEXA gives different values than calipers gives slightly different values than other methods.  Personally, I find it a little bit off that DEXA is putting someone who is at a BF% near death/their essential body fat levels (3-4% in men) at 9% but so be it.  And clearly DEXA is  measuring something else that is causing it to give these higher values.   I truly have no idea what (maybe someone in the comments can comment by leaving a comment)

Research has actually shown the above to be the case where DEXA is giving an estimate 3-6% higher than other body fat estimation methods in both women and men.

Consistency vs. Accuracy

But here’s the thing, you can’t compare apples and oranges like this.  The old caliper/visual/etc. estimates are giving one value (and what most, including myself are using) and clearly DEXA is giving different (typically higher values).  But they aren’t comparable.

In the series I linked to above, one point I make is that consistency is more important than accuracy.  Make no mistake, it’s nice to have a semi-accurate estimate of BF% or whatever but it’s only an estimate.  And even if two different methods are 5% different, it doesn’t make much of a difference in the big scheme in terms of estimating lean body mass (LBM) or calculating out diets.  It’s just not that big of a deal.

More importantly, the differences don’t matter because it’s an estimate no matter how you cut it.  More than that, being able to track relative changes is far more important than true accuracy.  So say that calipers put you at 10% and DEXA puts you at 15%.  Whatever.

And let’s say that you diet for a month and lose some amount of fat.  Calipers say you’re 8% and DEXA says you’re 13%.  Yes, the values are different but both dropped by 2%.  They both picked up the relative change (that is they are consistent) even if they give different values.

DEXA versus Calipers Redux

More importantly, and this was a question that I got regarding some information on the site, all of my early books and articles use the earlier values via calipers or visual estimates.  So in articles where I list some number, say 4% for a contest lean male or 10-12% for a contest lean female, that’s based on older methods.  DEXA might put them around 9% and 16-18% respectively but I don’t care.

Or there is my diet Category system which divides men and women into one of three different categories based on their BF% (which determines a lot of underlying physiology).  I use, 15% or whatever for Category 1 males.  DEXA would say 19-21% or whatever.  I’m using the older methods.

In the two books I’m working on, I will make the above more clear and provide values for both.  But again, to chortle “You’re not 8% b/c DEXA says some contest lean guy is 9%, lol” is missing the point.  The 8% is via the older methods, and the 9% is by a newer different method.

As my favorite author once wrote

“A man with one watch always knows what time it is, a man with two is never sure.”

Ponder on this until you understand and you might earn entrance into the Illuminatty.


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7 thoughts on “DEXA vs Calipers for Body Fat Estimation

  1. I was DEXA scanned last summer at 14.2%, and most of the comments in your forums estimated me at 7 – 9% (note, it was just an upper body shot, no back or legs…so this may have adjusted things a bit higher maybe around 10 – 11%). But I received some comments such as, “14%?!! If you lost any more fat you’d be dead.” Well, I’ve since lost another 3 – 4 pounds since then and no strength in the gym.

    I’m inclined to think the DEXA is fairly accurate, and since it’s an updated method, it’s simply able to pick up more body fat than a caliper would. I’ll try to pull up the study later, but DEXA was compared to the even more sophisticated four compartment model, which (shocker), was even higher than DEXA.

    The best I can come up with, is you’ve stated that 3% for a male is essential body fat that is in the brain/spine. My DEXA scan separated my percentages by body part, and my head had the highest percentage at 25%. This 3% essential fat could make up the discrepancy between older methods (you can’t pinch your brain with a caliper) and a DEXA scan. For example, contest lean bodybuilders that are near death would be 3 – 4% using old methods. Alberto Nunez is a famous example who is absolutely shredded before a contest, and was scanned around 6%.

    This is my long winded way of saying, a quick and dirty way of comparing the new and the old, would be to take 3% off what the DEXA scan gives you. So, an “internet 5 – 6%” would actually be a DEXA 8 – 9%.

  2. Here’s the thing: your SINGLE measurement notwithstanding, there doesn’t seem to be any consistently systematic difference and I make that statement based on someone in my FB group how owns a DEXA company and has done a lot of measurements. I used the contest lean for 8-9% as an example. Anyhow 3%, 4-6%, are you really gonna nitpick 2-3% when no measurement method has an error bar lower than that? Apparently you are.

  3. I believe DEXA is more acurated, and probably in bodybuilders the differences beetwen DEXA and calipers are because of visceral fat and other fat tissues (brain, etc). They probably has more visceral fat than regular people

    There is a comparison beetwen DXA and caliper formulas here:

    In my opinion, caliper formulas are quite inacurated (they understimate bodyfat, and this is obvious when you measure a man/woman with high bodyfat levels – the formula gives you really low bodyfat leves to an individual who looks like a pig)

  4. My point is NOT which is more accurate. Read accuracy vs. consistency subsection. My point is that you can’t compare the values and this nonsense chortling about “Oh you’re not X% because” is nonsense.

  5. No, I won’t nit pick over 2-3%. I realize from the James Krieger article and the studies referenced, DEXA can have a high error rate itself. Personally, I don’t put too much stock in my measurements, I track caliper/waist measurements myself, which are consistent. And use those to adjust my diet(s).

    Just out of curiosity, the DEXA company who posted on your FB page….did they note/report the error rates in individuals with their equipment?

  6. According to this article, DEXA values can be significantly impacted by a high carb diet prior to a scan.

  7. Lyle: What is your opinion on visceral adiposity in elite contest lean bodybuilders? Is that a reason for higher DXA-measurments compared to kaliper measurements?

    I have read an hypothesis that clenbuterol treatment leads to fat stores intramuscular instead of subcutanously and that is suported by use of clen in the meat industry where cattle is treated. I don’t know if it is true or not. Any clue?

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