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-   -   Dexa vs. Calipers for BF Estimation (http://forums.lylemcdonald.com//showthread.php?t=30841)

lylemcd 07-22-2015 08:00 AM

Dexa vs. Calipers for BF Estimation
 
Main site

alcahuetej 07-22-2015 09:57 AM

I also posted this in the comments section.

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%.

lylemcd 07-22-2015 12:16 PM

Yup, saw it on the main site. Same comment, a single measurement does not define the systematic difference; mine was only for an example.

As well, are you really gonna nitpick 3 vs. 4-6%

It's all an estimate for goodness sake.

VinnyG 08-15-2015 09:02 PM

someone posted that link on the comments> http://www.ncbi.nlm.nih.gov/pubmed/15162135

so i threw that formula on my spreadsheet and it returned the exact same value as the Joe Parrillo 9-site formula:

High-performance bodybuilding. J. Parrillo and M. Greenwood-Robinson. Berkeley Publishing group, NY. pp. 169-172.

lylemcd 08-15-2015 09:37 PM

So calipers about 3% lower than DEXA using standard equations if I'm reading it right.

About what's in the article, maybe a little less.

I'll have to get this full text

alcahuetej 04-08-2016 05:20 AM

I haven't seen this study posted yet.

http://www.nature.com/ejcn/journal/v.../1602131a.html

"Prediction of DXA-determined whole body fat from skinfolds: importance of including skinfolds from the thigh and calf in young, healthy men and women."

"CONCLUSIONS:

The results of this study confirm that lower body skinfolds are highly related to percent body fat in fit and healthy young men and women, and uphold current recommendations by the British Olympic Association to include the thigh skinfold with sigma4skf. Conventional use of the sigma4skf to estimate percent body fat is significantly enhanced by the inclusion of the thigh and calf skinfolds, either independently or in combination. In this group of males and females, the sum of the thigh and calf skinfolds accounted for the most variance in percent fat."

BenK 09-21-2016 03:19 PM

Great article. I had some issues with the results (like most people it seems) after having my DEXA scan. It seems they are using some altered algorithm to calibrate the results - basically if your report says "NHANES BCA calibration" you will typically have higher BF%

I've found this recently: http://www.bodydexafit.com.au/Body_D...le_athlete.pdf - last two slides describe the calibration and compare results with and without the NHANES.

lylemcdonald 09-22-2016 09:41 AM

Interesting, sounds like the BIA 'athlete' vs. 'non-athlete' setting or whatever.

But like all of this, athletes may not be representative of the general population and this probably throws the values somewhat.

alcahuetej 09-22-2016 12:36 PM

Quote:

Originally Posted by BenK (Post 295805)
Great article. I had some issues with the results (like most people it seems) after having my DEXA scan. It seems they are using some altered algorithm to calibrate the results - basically if your report says "NHANES BCA calibration" you will typically have higher BF%

I've found this recently: http://www.bodydexafit.com.au/Body_D...le_athlete.pdf - last two slides describe the calibration and compare results with and without the NHANES.

I'll have to check out those slides later. Maybe this is why my body fat kept coming up as 14% from the hospital's DEXA even though I was <10% (estimated 7 - 9 on both of these forums). I highly doubt their DEXA for bone density scans was calibrated for "athletes".

alcahuetej 09-22-2016 04:14 PM

I just checked my scan, and it used the NHANES method. By that method, a male bodybuilder is ~10%. I was 14.2% in 2013, and earlier this year 14.4%. Back in 2013 my trunk (upper abs and chest I believe) were the leanest at 12%.

That makes more sense.


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