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CRONA Study: Bod Pod Greatly Overestimates %Body Fat in Super-Slim Folks

Michael R

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Those of you who have been CR Society members and/or followers of the old CR Society email listserv may remember the CRONA study, a UCSF study on human CR that recruited CR Society members (overlapping significantly with Dr. Luigi Fontana's studies at WUSTL).
The study was intended to serve the diverse research interests of the investigators: most of the investigators, including Dr. Tomiyama (who was really leading the effort and responsible for subjects on a day-to-day basis) are psychologists, and primarily working in obesity and eating disorder fields, and wanted to better understand what makes long-term CR people so darned successful at maintaining fairly severe (by human standards) CR for years and years, when in practice the attrition rate from weight loss programs based on reducing *excess* Calorie intake (despite the fact that people on diets of the latter sort don't even "need" the extra Calories the way we do). Data on this were published in (1), which are now freely available in full-text thanks to the wise use of the tax dollars of American taxpayers.

However, the part that they talked up the most in their press coverage and in their recruitment efforts was the effect of CR on "telomere lengths," because telomere lengths are a very "sexy" area of aging research, at least in the public imagination.
Since many dieters experience a lot of subjective stress, and CR in humans, nonhuman primates, and rodents caused elevated wake-period cortisol, it isn't crazy to hypothesize that we might have SHORT telomeres; alternatively, of course, you might have expected that we would have unusually LONG telomeres as a result of a good diet and healthy lifestyle, or a CR-driven deceleration of the aging process.
in reality, the logitudinal data (studies following the same person over time) don't support an association between shorter mean leukocyte telomere length (which, everyone should remember, is what is actually being studied in all of these telomere length studies -- rather than critically-short telomeres and/or the length of telomeres in solid organs) and long-term health or survival outcomes (eg, (2-4). Also, many things that are bad for you (smoking, inflammation, overweight, physical inactivity, etc) shorten your mean telomere length in the short term — yet the effects wash out in the long term (4); that clearly shows that those things are not bad for you because they reduce mean telomere lengths.

It's n=1, but my mean leukocyte telomere lenthgths are unremarkable (and yes, I was of the opinion that it was an irrelevant market before I learned this ;) ; separately, long-time CR practitioner and all around great guy David Fischer got his leukocycte telomere length measured as part of a UK TV special, and it was dead average, even tho' he's a ~20-year CR practitioner with an excellent regimen and stupendous bloodwork, and who was estimated by one of the leading dermatologists in the UK to be in his mid-thirties when he was actually 51:

(If that isn't an embedded video, see the Dave Fisher CR video here).

We were given blood tests and a range of psycological and neurophysiological tests along with detailed verbal interviews on psychological matters, and they were quite up-front about what they were doing at every stage.

ANYWAY: One part of the study was to compare the performance of the Bod Pod (a device that is based on similar principles to underwater hydrostatic weighing but is done in an airtight chamber) to DEXA, the gold standard measure of %body fat. Several subjects who are very, very lean noted that our Bod Pod results were way, way out of whack to our DEXA results, indicating that we had the typical, excessive %fats of average Americans when in fact they are similar to or lower than Olympic athletes.

Now, those results have been published in free full-text,(4) and indeed, they found that Bod Pod does OK for the middle of the anthropometric range (tho' it's not great even there: see studies reviewed here), but at both extremes, it falls apart.
I was alerted to this study via an update from the investigators, which includes the following on the mean leukocyte telomere length and other blood data:

We are actually still in the process of examining the samples for a very comprehensive variety of aging markers. The delay is mostly due to us scraping together funding, and the complexity of first isolating subsets of cells (peripheral blood mononuclear cells), and then doing the very involved assays.

So: watch this space!
 1: Clues to Maintaining Calorie Restriction? Psychosocial Profiles of Successful Long-term Restrictors. Belsky AC, Epel ES, Tomiyama AJ. Appetite. 2014 Apr 16. pii: S0195-6663(14)00171-8. doi: 10.1016/j.appet.2014.04.006. [Epub ahead of print] PMID:24747211
2: Bendix L, Thinggaard M, Fenger M, Kolvraa S, Avlund K, Linneberg A, Osler M. Longitudinal changes in leukocyte telomere length and mortality in humans. J Gerontol A Biol Sci Med Sci. 2014 Feb;69(2):231-9. doi: 10.1093/gerona/glt153. Epub 2013 Oct 22. PubMed PMID: 24149432.
3: Mather KA, Jorm AF, Parslow RA, Christensen H. Is telomere length a biomarker of aging? A review. J Gerontol A Biol Sci Med Sci. 2011 Feb;66(2):202-13. doi: 10.1093/gerona/glq180. Epub 2010 Oct 28. Review. PubMed PMID: 21030466.
4: Weischer M, Bojesen SE, Nordestgaard BG. Telomere shortening unrelated to smoking, body weight, physical activity, and alcohol intake: 4,576 general population individuals with repeat measurements 10 years apart. PLoS Genet. 2014 Mar 13;10(3):e1004191. doi: 10.1371/journal.pgen.1004191. eCollection 2014 Mar. PubMed PMID: 24625632; PubMed Central PMCID: PMC3953026.

5: Lowry DW, Tomiyama AJ. Air displacement plethysmography versus dual-energy x-ray absorptiometry in underweight, normal-weight, and overweight/obese individuals. PLoS One. 2015 Jan 21;10(1):e0115086. doi: 10.1371/journal.pone.0115086. eCollection 2015. PubMed PMID: 25607661; PubMed Central PMCID: PMC4301864.

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Guest saul

Hi Michael!


I was in the third group in the CRONA study -- you were in one of the first two groups.


We were told that, measurements using the BodPod from the first two groups had indicated that the algorirhm that they were using to measure body fat on the BodPod was flawed -- so they simply collected raw data on that, not attempting to compute body fat from that data right away.


Some of the other tests recorded body fat in various regions of the body.   (I was personally delighted that my numbers came out the best in my group, in every body section).


BTW, my telemore lengh was also unremarkable for my age -- I think slightly shorter that others in the study within my age group.



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