The Value of Lab Values
Yesterday I challenged you to estimate my body fat percentage by looking at a recent picture. To be scientific about this little exercise I chose to reference as the correct answer the results of the “gold standard” hydrostatic weighing I had subjected myself to at the Malibu gym (it was actually a specialized truck that shows up once a year and performs the intricate and expensive underwater weighing tests for $60 each). 317 of you took a stab at guessing from the photo of me. It’s clear to me that many of you are quite good at estimating actual body fat levels (the average guess was 6.7%), but Gwen, anticipating the tenor of today’s post, took the prize with the closest guess at 12.5%… Ironically, that was also the highest guess of all and yet it was still a full 4 percentage points lower than what the actual “gold standard” test demonstrated. That’s right, my test score showed that I am 16.9% body fat. That’s 28 pounds of pure fat – if you believe the lab values. Even my wife Carrie tested lower at 13%. Am I really that fat? Probably not, but I went through this exercise to illustrate a point about which I will write today: that quite often, these so-called “gold standard” lab values are of little actual predictive value. Sometimes these tests are just plain wrong. And sometimes they can create far more problems than they solve. And if they are that far off when something is largely visible, what happens when they are dealing with more intricate hidden body chemistry? In this case, my jeans still fit loosely, so I really don’t care what the lab value was. I know the reality. But if I lived only by the lab values, I’d be inclined to start cutting calories immediately to lose weight.
In my estimation, medicine has become way too reliant on testing for lab values that reflect aggregates, population norms, cohort quintiles from dubious studies, or simple averages to arrive at reference ranges and the calculated risk factors that these numbers appear to represent. Even the term “risk” is deceptive, because an increase in risk for a disease doesn’t guarantee you’ll actually get the disease – even if you show a strong genetic predisposition (another test I wonder about). Sometimes the preventive or prophylactic treatments that follow such tests are useless or even harmful. Nevertheless, doctors often prescribe, biopsy, radiate, excise or otherwise operate based on assumptions they have made regarding your relative risk of disease – and sometimes simply on their relative risk of getting sued if they don’t follow the standard of care – based solely on lab values. We have spoken here often about how medicine is not “black and white” and how there is typically not a right answer to a medical issue so much as an educated opinion (or not) on a course of action. It’s my contention that your own opinion is often the most precise and valid. Certainly, use your doctor, but do your own research to be sure you make an informed decision.
Case in point, I had breakfast with a friend a few weeks ago who wanted my opinion on his recent blood tests and whether or not he should continue taking statins. Right off the bat I told him (as I am telling you now) that I am not an MD and am not allowed to advise anyone on any medical issues whatsoever. So we agreed to have a philosophical discussion (like we are having here now). He showed me the results of two blood lipid panels taken from the same sample (blood drawn in the same collection sitting) but that were sent to two different labs that same day. Of course, as I anticipated, no two lab values were the same from one lab’s test results to the other. Most notably, the total LDL differed by 40% from one test to the other. That’s a little disconcerting in itself. On both of these tests my friend’s total cholesterol was way under 200 and his HDL was over 100, which “philosophically” would put him in the lowest risk category for CHD regardless of which test was the more accurate. But my friend has been running scared his entire life because his father had a fatal heart attack at age 51. As a consequence, he has it in his mind that he needs to get the lowest LDL score he can possibly muster, come hell or high water and regardless of the notion that very low cholesterol levels are associated with an increased risk in overall mortality. He eats well (mostly Primal) and gets a lot of exercise on his road bike (in my opinion maybe too much) but he still lives his life in fear of what the numbers might represent. And he agonizes over which data set is the “real” one. At his doctors urging he has even been taking statins as a “precautionary and preventive” measure (and now complains of fuzzy thinking). We ended the conversation with my telling him, ironically, that his relative risk of death or disability from riding his bike 200 miles a week on those mean streets in an effort to protect his heart is measurably higher than his risk of having a fatal MI that might result from his pure cholesterol numbers. And his increased risk from the stress of worrying probably trumps them both.
I have mentioned my skepticism of lab tests in the past (Makes My Blood Boil, Weighing the Evidence: Science and Anecdote in Nutrition Studies). It started when, as anti-doping commissioner for the International Triathlon Union I was obliged to prosecute athletes for doping violations when their tests showed 4 or 5 billionths of a gram of a steroid metabolite at a time when the legal allowable threshold was “only” 3. A billionth of a gram could then be the difference between being labeled for life as a cheater or competing legally. Seeing how imprecise lab tests can be from one lab or one machine to the other, and how these wavy lines on sheets of graph paper could be interpreted so differently from one “expert” to the next, my skepticism grew. At some future date I will get into details regarding the many common diagnostic tests that are now being re-evaluated for their lack of effectiveness (mammograms, colonoscopies, CT scans, etc) but for now, if you want a really scary example of how nebulous lab values can influence serious medical decisions, go here and read what the National Cancer Institute has to say about using PSA values to diagnose prostate cancer and read the answer to question 4. Turns out the gold standard for diagnosing prostate cancer relies on a test for which it is acknowledged there is no “normal” or “abnormal” PSA. And that while the “over/under” lab value for a biopsy has historically been set at 4.0, 65-75% of men who have PSAs of 4.1-9.9 are found NOT to have prostate cancer. More damage is often done by the subsequent invasive test (biopsy) than by leaving things as is. Meanwhile, 15% of men biopsied with PSAs below 4 are shown to have prostate cancer. As many docs say, “it’s not much, but it’s the best we have” in diagnosing this serious condition. True, but little consolation when you risk losing sexual function as a result of an invasive biopsy which is, in turn, a result of a nebulous lab value.
Anyway, back to my personal example. Why was my body fat test so far off (if in fact it was)? Who knows? I can estimate it on website calculators and get closer to what I think it is. Like this one… where I come in at 8.68% (I do like that number better). With some tests like skinfold and hydrostatic weighing, there is an assumption that the exact same data (skinfold thickness or underwater weight) when applied to older people (I’m 56) reflect a naturally higher body fat for some reason. But when I researched how they actually got the original data they use to estimate body fat, I found that it was largely from autopsies performed in the 1860’s and 1870’s. Not many autopsies have been done for that purpose since. Also, the reference data on skinfold tests and hydrostatic weighing still assumes that as you get older, you automatically lose muscle (regardless of how you eat or how much you work out) and that your skinfold thickness decreases so much that the same lab value at 22 years of age represents twice the body fat at 56. Hey, since 50 is the new 30, maybe those lab values are obsolete, too?
By the way, the gal who administered my body fat test, and who has done thousands of these, had guessed me at 8% before she started the test. She was so flustered by my results, she insisted on doing the test again. And then once again. And then simply handed me my $60 back and said, “I have no explanation, but clearly your test is way off.” Frustrating. But this sort of thing happens every minute of every day in doctors’ offices and clinics throughout the country. Except the doctor doesn’t acknowledge it and you don’t get a refund.
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Posted By: Mark Sisson
Mark
They probably did not calculate the residual volume in your lungs correctly. Any air left in your lungs will increase your buoyancy and will register as fat. In order to get an accurate hydrostatic weighing measurement, residual volume has to be measured. THis is done with some type of gas dillution technique. My guess is that they estimated your residual volume from a table, based on your lung vital capacity (which is easy to measure). Then they look it up in a table. Sometimes there can be a big error in that estimate, over or underestimating your bodyfat. Sometimes “eyeballing” it is better.
Mark,
Have you ever had a dexa scan to determine your body fat vs lean muscle composition (it also calculates bone density. It does require the subject to be irradiated and is only reccomeded once every 6 months by the MD’s who own the practice (and the machine) where I work. It was only $40 per scan. My research found it was supposedly more accurate than the under water testing. We recently had a “biggest loser” contest at our crossfit affiliate and used this method to determine numbers. There were a couple of results that didn’t seem to fit, but otherwise seemed accurate. Your thoughts?
As a diabetic I live and die by my lab results either my every 3 months A1c or my every morning (noon and night!) finger stick. I have also started watching something else though -How do I feel? Fuzzy Headed? Tired? Depressed? Clear? Energized? Moving Forward? I know that lower blood sugars mean a longer healthier life but short-term, if I feel like crap I need to look at what I have eaten lately and how it makes me feel.
Mark,
Besides the most obvious rational for the high BF, the parameters utilized to assess the raw data, what about internal fat deposits. With your diet and activity level it seems remote but many individuals are not fat outside but carry large amounts of fat internally which puts them in even greater risk of dis-ease and mortality.
Love your Blog.
I don’t believe that someone who so obviously has little externally visible fat would have dangerous amounts of internal fat deposits. The very premise of Mark’s Primal Blueprint is that this fat would be stripped away just like the rest of it. Why would that fat stay? Does the body pick and choose? I doubt it. Sounds like CW spot reduction theory to me.
I have been using the Tanita body fat measurer and if I am dehydrated (if I weight in after a run) I weigh less but my body fat goes up. When I drink 16 oz within 5 minutes and reweigh, my weight goes up and body fat goes down. I dont even think these can be used consistently even though they are off, particularly for women. I simply use my jeans, and use strength increases to determine if I are getting leaner/building lean muscle mass. Ihave weighed the same since 1989, but I started doing sprint-IM tris in 2000, and don’t really care what my body fat % is. (I guess it is about 13-15%).
Weird. My home scale calculates me at 24%, but the Tanita hand held at the gym says I’m 16%…I’m a woman and I think I’m closer to the 24% but seriously, why the huge difference?
Don’t know if anyone has mentioned this yet, but my trainer at the gym is very lean and he always tests high too. Someone told him that unless you can completely expel every bit of air from your lungs that it can make a huge difference. And just because it feels like your lungs are devoid of air doesn’t mean they are.
Obviously, some people would be better at doing that then others.
When you write that article, I’d be happy to proof read it for you. I’m a Biomedical Service Engineer, so I know those machines very well indeed. You are quite correct, they work within tolerances and may I say that a moving van would screw the calibration on that machine. Each time a hospital unit is moved they need real calibration, not just the software calibration…
Tanita scales and Garmin (+ other HR monitors) are also very suspect, all you have to do is compare the price of these cheap and nasty items with plus/minus 10-20% tolerance, with real medical devices (costing thousands) that do the same thing and are correctly serviced and maintained. Note my emphasis there.
Personally I go by how I feel, and are my size 4′s (USA size) tight or not.
Most people are quibbling over the BF test without addressing the issue of lab values. Probably because we just accept them as scientific rather than questioning. The best advice is to stay AWAY from the doctor unless its an emergency. Solve all your problems through diet and alternative medicine and be your own medical expert.
I personally think bodyfat percentages are inaccurate in the main and a false measure of health. They have no correlation to athletic performance either. They just became a fad because of bodybuilders who look great at low bodyfat…the caveat is they are very unhealthy at the moment from thyroid meds,diuretics, etc to achieve the “look”. In fact evidence suggests hormones are unbalanced when bodyfat is too low.
like any measurement, it depends on the tester, norms and standards, where you store the body fat, what kind of fat it is…and some other factors…this is also more important than the # itself that many get caught up on.
i’ve tested over 5000 people using skin calipers and 4, 8 and 12 point site measurements (and still think there are flaws to it, but if done by same person many times it gets more valid)…these results have been correlated with other diagnostics to have some intersting parallels with overall endocrine health and fitness ability…so the # should not be the focus…it should be where you sit based on that # and if you need to or want to improve.
I have had many men for example lean in the mid section but store a lot of fat around their pecs which was correlated over and over with low T and DHEA levels…very intersting considering one would think b/c BF around the mid seciton was low that they were “healthy”…anyhow…follow the advice on living on Mark’s site and you’ll improve whatever you want in the BF area without worrying about the number….afterall, worrying causes more BF storage at the mid section…a bad cycle
Great post and thanks for the information, Mark.
Has anyone ever tried the “BodPod”? At my old gym in Washington, D.C. they had this egg-shaped apparatus that is supposedly the most accurate measurement of bodyfat.
Yeah there’s a BodPod here at Cal State Long Beach. I was measured at 7.6%, but my friend, who is also very athletic was over 22%! we were really confused at his result. Hydrostatic is supposed to be better actually, but from Mark’s results it can clearly be way off.
For reference here’s a pic from around when I was tested;
http://forum.bodybuilding.com/photo/showphoto.php?photo=107078323&ppuser=109191823
A friend of mine turned 31 just the other day, according to the chart, he gained 1% bodyfat overnight.
Just because there is some magical border you cross when you go from 30 to 31…
A correct thyroid panel is this
TSH, Total T3, Total t4, Free T3, Free t4, Reverse t3 and thyroid antibodies.
This morning I teseted 9.7% on my Tanita. I could only wish for such a result (‘m a 65 year old man). Don’t worry Mark the only valid bf test is autopsy. Our time will come for acurate results, in the mean time I don’t concern myself with the value of readings only trends.
Thanks for all the info….my doctor says my cholesterol is high but I feel better now than I have in 15 years or more….thanks to eating Primal and supplements. My blood pressure is normal for the first time in more than 20 years. I only take 2 presription medications now…instead of 6. My son got me interested in Primal eating from Marks site. And oh yeah……I love my Vibrams……Thanks Mark ! TWIGS!!
Thanks for all the info….my doctor says my cholesterol is high but I feel better now than I have in 15 years or more….thanks to eating Primal and supplements.I am 61 years old and my blood pressure is normal for the first time in more than 20 years. I only take 2 prescription medications now…instead of 6. My son got me interested in Primal eating from Marks site. And oh yeah……I love my Vibrams……Thanks Mark ! I have given myself a new nickname thanks to Grok. It’s…..TWIGS!!
Hah, I bet the test was just measuring all the yummy fat you’ve been eating with your diet (^_^)
Get a DEXA done. The low radiation is worth the segmented values. I would have had you at about 6.5%
Blood tests are usually not very accurate for what is happening in the body. Saliva, stool and urine testing is always more reliable and predictable for real results. Many vitamin tests per blood are not good as you need to get RBC analysis to get accurate levels in the body. The best labs out there for accurate testing are ZRT for any hormonal testing, Genova Diagnostics for leaky gut and other stool tests and Metametrix for vitamins and candida. All these labs also offer a mulitude of tests and some are well noted for the best in the buisness. Doctors Data is great for heavy metal testing. Sad thing about all of this is that most of this is not covered by insurance as it does not necessarily follow the American Medical Model as we know it today. A good naturopathic doctor is by far the best way to go as they are set up with all of these labs and will know what to order, but once again usually not covered by insurance.
A B-complex is very important and you should have your Vit D level tested, this can be by a regular doctor and through blood.
Blood tests are usually not very accurate for what is happening in the body. Saliva, stool and urine testing is always more reliable and predictable for real results. Many vitamin tests per blood are not good as you need to get RBC analysis to get accurate levels in the body. The best labs out there for accurate testing are ZRT for any hormonal testing, Genova Diagnostics for leaky gut and other stool tests and Metametrix for vitamins and candida. All these labs also offer a mulitude of tests and some are well noted for the best in the buisness. Doctors Data is great for heavy metal testing. Sad thing about all of this is that most of this is not covered by insurance as it does not necessarily follow the American Medical Model as we know it today. A good naturopathic doctor is by far the best way to go as they are set up with all of these labs and will know what to order, but once again usually not covered by insurance.
It doesn’t matter what test you use, and the numbers are pure superfluousness.
What’s important is that you use the same test over and over again as a reference.
If you use the calipers stick with calipers and stick with the same guy/gal that’s testing you.
The bottom line is what are you goals. Do you want to be super fit? Do you want to look like Brad Pitt from Fight Club? Do you want to look like a Spartan from 300?
Look in the mirror, measure performance with your own metrics (500 m run? deadlift? pull-ups?), and ask yourself how you fee. That’s more important than your body fat %.