Are DEXA scans ACCURATE? What YOU NEED to KNOW: | 26 - Healthspan Medicine #5

[@robertdaymouse3784]

Thanks for taking one for the team and getting two Dexas in one day. I would suggest there is a strong inverse relationship between those that get Dexas and those that would benefit the most from Dexas.

[@Krunch2020]

The VAT cannot be explained away. Either these scans are garbage or they are garbage.

[@drron10]

Water or hydration changes the lean numbers significantly. DEXA must be done fasted with no liquids. Was that the difference?

[@yiannis.demetriou9696]

What if you wake up and your urine is dark orange wouldn't that alter the results?

[@aroundandround]

In my experience, DEXA scans are hardly the “gold standard” they are made to be for body composition. They may give you similar numbers on repeat scans the same day but there’s far too much variation across different machines, so there’s no ground truth for the absolute numbers, only a sense of relative changes across measurements on the same machine, which is not that different from the sense you get with a tape and mirror that are the ultimate ground truth that matters. DEXA scans are much more reliable for medical grade lumbar and femoral bone density measurements (unlike body composition) because the population normalization needed to compute deviation scores is more reliable and rigorous.

[@ChessMasterNate]

I don't think sub 10% fat is a worthy goal. It is not correlated with anything beneficial. Optimal is probably 12-17%...for guys. Achieving/Maintaining bone density, muscle, strength, endurance, coordination, flexibility, balance, isometric endurance, high intensity performance, lung volume, diaphragm strength, core strength, muscle control, reaction time, short term memory, working memory, long term memory, ability to visualize, mental math, vision, hearing, smell, oral health, breath holding, skin elasticity, ability to withstand cold, hot, hot+humid, low depression and anxiety, comprehension speed (helps to watch videos at 2x), prediction of kinetic motion, accuracy of emotion perception, predicting pet behavior, maintenance of skills (foreign language, musical instruments, martial arts, intellectual board/card games (Chess, Go, Bridge), use of software, computers, programming, use of complex tools like tractors, lathes, and mills, operating various kinds of vehicles), welding, and repairing things well, are worthy targets. Different people would have different skills. I think people should learn a few skills they enjoy, where the opportunity to exercise those skills is not contingent on having a job performing them. You want skills you can continue to do after you retire to keep your mind, and ideally, your body, active. My grandfather had a machine shop under his house, and repaired and built things, and he played chess with other retired engineers. They, too, would tinker with stuff and show what they were working on when they came over. My grandmother maintained her cooking skills, gardened, painted, sculpted, wrote poetry, made jelly and preserves, and corresponded with at least 50 people in letters. Every Christmas, she had dozens of Christmas cards she received that she would put on the horizontal louver blinds. Oh, and she knitted too. And she did not do anything halfway, either. She had an art studio in Balboa Park, and she went to a club where women did poetry, entered contests... They also played Bridge with other couples weekly. And we don't like to talk about it, but we need to maintain basic skills too, or we risk having to be institutionalized.

[@ericquek673]

Matt, thanks for those data and reviewing them. For MOST of us --- more realistic ways are: a)weighing ourselves on weight scale or b) go to gym where there is what is known as BIA. Bioelectrical Impedance analyzer. Yes, it is not as accurate as DEXA. Nevertheless, that would be more practical, can be use to track progress in terms of VAT and lean body mass, and muscles. It would be nice if you had done that as that is more practical .

[@nicholasarapis]

Totally agree. In the video I talk about using tape measurements, photos, and a weight scale to keep track of body composition in between my annual DEXA. Matt mentioned he used a BIA scale regularly.

[@markmanson1913]

For many people like myself bias inaccurate as it is based on ab algorithm . Have done bia then default big variation others have found the same

[@ericquek673]

@@markmanson1913 It boils down to what are your goals & expectation understanding drawbacks of each device. When Nicolasarapis replied Matt uses BIA on a regular basis tells you alot. I too use BIA once or twice a month. Why? I understand the limitations of BIA: Hydration level, recent food intake, exercise before or after using device affects body hydration & blood flow. BIA cal. based on generalized assumptions about body shape and composition especially with atypical body types . Algorithms used calibrate on specific pop. like healthy adults. DEXA: Expensive, cant use to track routine fitness ---my purpose for using that as a guide . radiation exposure. Most dont know this: OPERATOR SKILL---accuracy of DEXA can depend on the skill of the operation, particularly in positioning the subject and calibrating the machine. Time consuming about 20 minutes vs less than 5 minutes. Bottom line: Ease and non-vasive, can be used frequently for rgular mointoring of body comptoistion in fitness. My point when I commented originally was that it would be beneficial for Matt to have include BIA in more detail and compare and contrast. I understand why he did not due to time constrain and other reasons. It was an informative session for the lay public though.

[@ats89117]

I guess it's good to be a bonehead!

[@DJhunhu]

Nicolas, how are you determining that you have “enough” muscle mass for maintaining it through the rest of your life (into elderly years)? I’m around your age with what a appears to be a similar amount of muscle mass and athletic history with weight lifting where I’ve also had elite level VO2max readings in the past (above 70ml/kg), keeping it high through my 20’s and early 30’s (doing well in obstacle course and mountain racing), but have been thinking to continue being focused slowly accruing muscle now through age 40 or so, then re-shift focus back into VO2max training of various protocols and low end cardio accrual of minutes per week that has a wide range with decreasing overall mortality risk. Obviously doing both resistance training and VO2max training is optimal, but there’s only so much time and energy with other life priorities, leaving me to wonder, “What’s this “enough” that Nicolas is mentioning here based on the calculations or clinical judgement?” Any references you could support with this rational would be appreciated. 🙏 Thanks for the clarity when you can:)

[@nicholasarapis]

Hey DJ, my goal is to maintain 95 percentile (or better) for my AMLI and FFMI. This is somewhat of an arbitrary number, but I picked it because I have been lifting since I was 12 (32 now) and I can tell ~95% is the most amount of muscle I can hold onto naturally and while balancing family and work. Peter Attia recommends his clients to aim for a minimum of 75th percentile. I’d say this is a good place to aim for people who are below the 75th percentile. Same goes for VO2 Max. If you have similar muscle to me and a VO2 max around 70ml/kg then I'd say you're doing great! Shows that you've developed a well-rounded exercise routine that includes weight training and cardio. If I were you, my goal going into your 40s and beyond should be to maintain (or increase if you're lucky) those numbers. Because you’re already elite in both ALMI and VO2. We can use studies to see the correlation between grip strength, muscle mass, and VO2 max. For the most part, the higher percentile the better. Though there are examples of people overdoing cardiovascular training or strength training and it having a negative effect on longevity. But from what you've told me, I think you and I are both in the "goldilocks zone". VO2 Max and Longevity - www.imrpress.com/journal/FBL/23/8/10.2741/4657 ALMI study - www.ncbi.nlm.nih.gov/pmc/articles/PMC5398591/ Grip Strength - www.ncbi.nlm.nih.gov/pmc/articles/PMC6778477/

[@ZoeyKs]

When I get a DEXA scan to measure my bone density post-menopause, I only get the bone density scores and nothing related to body composition. I wonder why. Is the body composition part done automatically and, if so, do I need to be asking for a different report or documentation of the scan?

[@chrisgiles5653]

My DEXA report doesn't mention VAT - would it be the same as android fat mass?

[@SilverFan21k]

3rd