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.

TAGS:  Big Pharma

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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73 thoughts on “The Value of Lab Values”

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  1. Very interesting Mark. I went through the same skepiticism last summer.

    Curious what my BF% is I had a seasoned caliper tester meaure me at 14%. I thought that was pretty high. So, I signed on for a “dunk test” in the truck like you did 2 weeks later. Weighing exactly the same they measured me at 4.4%. I was like “c’mon, I am lean, but I don’t think that I am that lean.” My best guess is that I am 7-8%.

    The guy who tests people for a living thought I would be about 6-7% upon visual inpection alone.

    Like you, I am skeptical of it all.

  2. I believe its Tamita that makes a scale to determine bf, but wait there is one reading for “athletic” people and one for “normal” people. Totally bogus if it could actually measure anything. Many gyms bought theseand then found out how worthless they were. The electrical impedance measures water in the body and the more water the leaner you are..the theory. The mirror is the best judge.

  3. I tested at 8% body fat in September, and from the pictures on this site, I’d say we’re pretty close to the same leanness. 16% is ridiculous.

  4. could they do your measurements and run your numbers as if you were 25? Would that have changed the results since the +50 yrs assumptions would no longer apply?

  5. What about the electronic ones that measure resistance? I though those were the most accurate, since fat has a known resistance. I could never figure out how you can stick someone in a tub of water to measure fat anyway. I always thought displacement was displacement.
    It doesn’t matter anyway. It’s how you look and how you feel that counts.

    1. Kaiser uses something like this to measure bodyfat. You stand on a scale and grab the handles and wait for the printout. It had me at 25%!

    2. I’ve always thought those were bullshit, since the largest resistance in your body (by far) is your skin. If the resistance of your skin varies just a little bit from the expected values (which it would, depending on all sorts of factors from how much callous you have, how hydrated you are, etc.), those variations would overwhelm the much smaller variations in resistance due to fat content.

      Now, I’m a mechanical engineer, not an electrical, and I don’t know if they have ways to mitigate that error, but it just seems like a REALLY unreliable principle to rely on for accurate calculation of something with so many factors involved.

  6. At 50 years old, I my results are around 11-12% bf using a clinical impedance apparatus, and the same when I get my Bio Signature done (calipers, Charles Poliquin method). But looking at myself, I know I’m much lower, thanks to a paleo diet and intense exercise.

    Regardless of the accuracy of these tools, I think they can still be valuable. Measurements are useful directionally – to show whether your making progress or not.

      1. As long as it’s consistent with its inaccuracy – ALWAYS measuring 4% too high, for example – you can still use it as a guideline.

  7. Oh how those numbers can mess with you!

    I got dunked a few years ago and came out at 24%. I thought that I would be higher, but whatever.

    Fast forward a couple of years. I got dunked again after eating paleo/primal and doing crossfit for a while. I KNOW my body is different–more muscle, less fat. A lot different! But my second dunk showed 23%. I cried, of course.

    The lady offered to dunk me again after I gave myself a week to practice the breathing technique needed (that kind of freaked me out!) A week later I showed 22%. So definitely there is some ‘human error’ involved (mine! I could never exhale all the air out of my lungs.)

    So I don’t get dunked or get on the scale any more. I go by how I feel and how my clothes fit. As long as I don’t have a muffin top in my jeans, I’m happy! 🙂

  8. At close to 16% BF, you will hardly see your abs, let alone your obliques. Mark, you should be closer to 7% BF range. If you lose some more BF, you should see your pancreas make insulin. That should make an interesting post!!

  9. If I use a one caliper approach which measures at by the navel, where my fat is the last to come off, then I’m projected in the 20’s, but various websites put me in a 3-site measurement at 10-15%. Go figure! It’s all so subjective, even with instruments apparently. I like arthurb999’s recommendation – use the mirror or verbage. “Damn he looks fine” out ranks any scale I’ll ever use!

    1. Yeah, don’t you have to eat a lot of wheat for several weeks for the test to be workable? That’s what really scares me away from taking it; I know wheat makes me feel cruddy and I don’t want to damage my body with all that starch, let alone gluten. So I just eliminate wheat and forget about the test entirely. Of course, the doctor chides me because there are apparently some mysterious wheat-exclusive nutrients that I’m missing out on. Oh well, time for a new GP, I s’pose.

      1. Plus, you know, it doesn’t really matter if you have celiac if you don’t eat grains anyway!

    2. Wow, does anyone know anything about this subject???My daughter just diagnosed with Celiac. She ate practically perfectly for 3 months, went back for the test her levels were even higher ( thought as her mother that we would be “acing ” the test with hugely different numbers). Then we did a food diary for the Yale Dietician. Her only help was possibly some rogue cross contamination or too much dairy??? Any comments or ideas would be so appreciated. I trust people like you than I do the Gastro doctors…any comments or ideas ????

  10. Very interesting! Did the test use your age in any part of the calculations?

  11. Kudos to the technician for giving your money back.

    TSH is another less than predictive test IMO. Unfortunately, my fiance was diagnosed with fibromyalgia over a decade ago. Despite the overlap of symptoms with thyroid disorders she has had only TSH, T3, T4 and ultrasounds of her thyroid. Since her TSH is in range that ends their curiosity, despite her thyroid being larger on one side.

    1. You are right. Thyroid disease is often a sign of too little iodine and resulting symptoms. Research a product called iodoral for iodine and incidentally its a potent antifungal. In addition vitamin D levels are now routinely checked and most people need to supplement at least 5,000 IUs a day to keep autoimmune diseases away. UCTV has a lecture series on vitamin d and the best is Vitamin D and chronic illness. I truly believe that an adequate intake of vitamin D and cutting out sugar in all forms would heal the world of most modern disease.

      1. There’s also ‘Lugol’s Solution’ for iodine. It’s been around for a loooong time 🙂 If you Google it you’ll get a bunch of info.

        Hope it helps.

  12. You raise an excellent point about how having too much confidence on numbers and medical tests can be misleading and can actually cause us harm if we place too much reliance on them. This idea is discussed at length in a relatively new book called “Dances with Chance” (no, I have no connection with it — I just want to give credit because its not my original thought).

    One of the more interesting findings was that a doctor’s prediction using medical tests and records about how long someone would live was less accurate that simply asking the patient to rate their own health from Poor to Excellent on a five point scale. More information is not “better” information. (The “use the mirror” comment is right on.)

    After reviewing a host of data re medical testing, the authors conclude: (1) one should generally stay away from doctors unless one feels sick; (2)when one becomes a patient, one should recognize the inherent uncertainty of medical science; and (3) make yourself as informed as possible about any diagnosis, test or treatment you may receive, and especially its limitations.

    Which is a long way of saying: You look great (and I assume you do feel great too), so who cares what the test said?


  13. I did not get a chance to guess yesterday, but with your clearly visible abs at all times (and not just flexing to make them come out), you are obviously 7-9%.

    Now my guess is based on a guide that I saw somewhere once and saved to a Word doc that relates what a man looks like at certain bodyfat percentages. I am 18% myself and yup, I am exactly as described in this guide, ie “15-19%, visible muscular definition in the shoulder and arm areas, but absolutely no abs”.

    Interestingly, I use no skinfold calipers, hydrostatic tests, impedance or any other high tech method. I rely on a simple equation, gender specific, that I found a long time ago. Simply plug in your waist size and bodyweight. In my case, 236 pounds and 38.5″ waist (I’m working on it!!)spits out 17.8% to be exact. Looking at Mark and knowing that he is 165 pounds, I worked the equation backwards and guestimate his waist to be right around the 30″ mark. That would give a BF% of 7.7. Works for me.

  14. Just to add to my previous reply, here is that equation I use:

    The percentage body fat is calculated for males as 100*(-98.42 + 4.15*waist – 0.082*weight)/weight and for females as 100*(-76.76 + 4.15*waist – 0.082*weight)/weight.

    The argument made in favor of this (as I recall the author making) is that it allows for a more accurate measurement of the loss of visceral fat. Skinfold measurements are just estimates of visceral fat levels and even they, again according to the author, are subject to hydration levels (possibly skewing results)and the usual accuracy errors relating to skill or lack of on the part of the person measuring.

  15. Just for the fun of it Mark go and get a body fat test done with the DEXA, supposedly more of a gold standard than underwater weighing. Might be interesting. For that matter do it all ways possible and post the scores you get. Dexa, hydrostatic, calipers, electrical mpedence, bod pod, etc. That would be interesting.

  16. 16.9%! LMAO!

    If you’re 16.9%… then I’m 30%. At least the number is so far out there that you should be getting a good laugh out of it.

    I guess it wasn’t a lab, but I’m surprised you didn’t mention your caddywhompus blood pressure testing numbers from a while back.

    You’re just a weird, fat, sickly man Mark! Get over it 😉

  17. Mark,

    You have at least two factors that argue against a successful test of the sort you participated in:

    1. Practical age based on your actual body composition versus chronological age;

    2. and, muscle weight.

    I didn’t realize such tests were age-graded as you imply, but these tests do a miserable job of measuring muscular atheltes.


  18. How much of the fat percentage determined by hydrostatic weighing is internal fat as opposed to subcutaneous fat?

    Since muscle contains more water than does fat (which makes fat more buoyant than lean tissue in water) then the difference in bodyweight measured in air and then in water should give the total body fat (via computation). But having any air in the lungs (or maybe being over/under hydrated) would affect the accuracy of the readings.

  19. I can’t believe the “Gold standard” could be that far off. Unreal. You don’t even BEGIN to see any hint of the OUTLINE of ab muscles until about 12% bf. You have a full 6 pack going, and extreme definition in the obliques. I think anyone who understands what different bodyfat levels look like, anyone knowledgeable about it would peg you in the 6%-7% range. Don’t let that stupid test mess with your head. You KNOW it’s bogus. It’s insulting.

    I have a tanita bodyfat scale at home. And for 6 weeks, I went DOWN in weight, and UP in strength in all my lifts at the gym. I didn’t just start lifting so it’s not ‘beginner gains’ – I continued to make progress in routines I had been doing for several months. Up in strength, down in weight, you HAVE TO be losing fat and gaining muscle. Not according to my scale. The BF reading stayed the same over 6 weeks as I lost 5 pounds. That would mean I lost 5 pounds of muscle.

    It REALLY messed with my head! “Am I losing muscle? How could that be, I’m eating enough protein, but I do look kinda’ skinny. But wait, how can I be getting stronger then? WTF is going on?” All because of this stupid scale. If I hadn’t used the scale I would have known I was doing great, dropping pounds AND getting stronger? Are you kidding me? That’s the holy grail of changing your body!

    My experience is any kind of measuring equipment can lie. The MIRROR CAN LIE. You see yourself in it daily, if you start thinking “well maybe I AM loosing muscle” you can make yourself see whatever you want to see looking back at you.

    What doesn’t lie is PICTURES. Take pictures in the same spot with the same lighting, and then compare them over a reasonable amount of time, like month-to-month. The pictures won’t lie like the mirror can. When you pull 2 pics of your body up on a computer side by side, you can tell what’s going on. That’s how I measure my progress now.

    1. Pictures are a great idea. I think sometimes the mirror can be unreliable because even our mood can alter our perception of what we really look like. Seeing a month-to-month picture can help bring that body image back to a realistic range.

  20. I didn´t read the responses, but I am guessing that no one thought about visceral and sub-cutaneous fat. Marks subcutaneous fat is probably around 7% and the rest is visceral, which is not noticed as it surrounds his organs, in his brain a various other places besides under his skin which are not measured with calipers.

    1. Visceral fat surrounds the abdominal organs and is especially noticeable when it hangs around the kidneys. It is responsible for the beer belly look that men often have. Subcutaneous fat mostly hangs around the thighs and buttocks, and is responsible for the pear shape that many women tend to have.

      Obviously, as demonstrated in the above picture, Mark does not have a beer belly.

  21. So weird. Using the calculation above, submitted by Christian, I’m 21-22%. Yet, my BMI is 29 and I’m nearly obese by those standards. My Body Fat scale has read all the way up to 39%. Bad day. Stopped using it after that. Weighing in at 185 lbs., female, 5’7″, it sounds like I’d be hugely overfat. I’m surprised at the calculation that’s for sure.

  22. Over the past couple of years I’ve been measured, using the hand-held resistance devices, between 25-35% body fat.

    I’m 5’6″ and weigh 120 pounds.

    It would be comical, except that my employer determines how much I pay for health insurance in part on my my measured body fat pct.

  23. Fixed Gear,

    Right on. I agree 100% with what you are saying. Now further to my earlier replies, I did find that guide (this applies to men only) about what you look like at certain bodyfat percentages. As I now recall, this came from a bodybuidling type forum:

    1. Full House = No visible muscle definition. Bodyfat level = over 20%.

    2. Hard = Some muscle separation appears between delts and upper arm. Abs are still not visible. Approx. bodyfat level = 15-19%

    3. Cut = More muscle separation appears particularly in the chest and back, outline of the abs begins to appear slightly. Approx. bodyfat level = 12-14%

    4. Defined = Muscle separations get deeper in the arms, chest, legs and back, and abs appear when flexed. Approx. bodyfat level = 10-12%

    5. Ripped = Abs are clearly visible all the time, vascularity in arms is prominent, chest and back separation is obvious, and face is starting to appear more angular. Condition can be held indefinitely. Approximate bodyfat level = 7-9%

    6. Shredded = Striations appear in large muscle groups when they are flexed. Vascularity appears in lower abdomen and in the legs. Condition can be held for several days with careful dieting. Approximate bodyfat level = 5-7%

    7. Sliced = Muscles and tendons begin to appear in the face when chewing, striations appear everywhere and vascularity appears everywhere. Bodyfat levels are close to 3% and subcutaneous water levels are near 0. Condition can only be held for a few hours at a time. Not a healthy condition to stay in due to lower water level.

  24. Bravo! I am so glad you wrote this post…not that you tested higher than you anticipated but that you are bringing light to the inconsistency of medical testing 🙂
    I work with women who have eating disorders, testing and numbers can control the lives of people who have distorted the importance and actually the validity of these tests. Living by the numbers is a drab and inaccurate way of leading ones life.
    The more we can show how the medical values are not absolutes the sooner we can help people move beyond black and white thinking.
    Love your site and dedication Mark!

  25. 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.

  26. 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?

  27. 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.

  28. 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.

  29. 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.

  30. 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%).

  31. 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?

  32. 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.

  33. 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. 😉

  34. 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.

  35. 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

  36. 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.

  37. 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…

  38. A correct thyroid panel is this
    TSH, Total T3, Total t4, Free T3, Free t4, Reverse t3 and thyroid antibodies.

  39. 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.

  40. 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!!

  41. 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!!

  42. Hah, I bet the test was just measuring all the yummy fat you’ve been eating with your diet (^_^)

  43. Get a DEXA done. The low radiation is worth the segmented values. I would have had you at about 6.5%

  44. 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.

  45. 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.

  46. 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 %.

  47. The variability of tests also has a lot to do with calibrations and universal standards. Is there a recognized standard to use for BF testing where the performance of different methods can be compared? No.

    This is true for hundreds of tests. If you try to compare from one lab to the next there are many potential sources of variability and only one of those is clinically significant biological variation. (Some biological variation is NORMAL, to be expected and is NOT clinically significant.) One of my big issues with most doctors is that they think lab tests are the end all/be-all when at best they are point-estimates. And a big picture evaluation is required to properly interpret their meaning.

    Hmmm, this sounds cranky. I need to get to bed!

  48. I am a 53 year old male. I was skinny (130 lbs.) until I hit 35 years old. I have a “Health O Meter” by Sunbeam that I have used to weigh myself for a few years. It says my BF is 20.1%. A year ago before eating primal at 174 lbs., it said my BF was 25%. I have lost a total of 24 lbs. since starting my primal diet. I went from a high of 174 lbs. to my current 149. I still have a little teeny bit of belly fat just under the belly button. I don’t necessarily believe the 20.1%. I should mention that I do not exercise at all.

    I don’t think I wanna lose more weight as I think I look pretty good and really do not want to look gaunt but I do want a flat stomach with some visible abs. So is exercise the answer here? Should I try and lower the BF percentage?

  49. I recently had a blood pressure scare from something that must be very common. The typical blood pressure cuff in a home blood pressure monitor or the automatic one at the drugstore is only rated up to about 13 inch circumference for the upper arm. I was getting results 20 or 30 or more points high by using a cuff that was too small for my arm. When I got a bigger one, using the same gauge, bulb, etc. the results seemed more reasonable, and consistent with what I get at the doc’s office, where he has more than one size of cuff, and a nice, simple manometer to read the pressure on. (Pretty hard for a manometer to go out of calibration.)

    Anyway, if you don’t like the blood pressure numbers you’re getting, check the rated arm size of your cuff. I suspect any large person who does strength training will be above the limit. Or perhaps anyone who’s obese enough, not sure if this is comparable. I’m a bit of both.

    Staying away from the doctor is dumb. They really can do a lot of stuff to help you. Yes, the system is deeply flawed, but if I hadn’t been to the doc I wouldn’t know I had diabetes, though of course I knew there was some risk. Plus, the doc can keep you up to date with your vaccinations, even more important now that the anti-vaxers are causing an uptick in some diseases. Maybe my mother would be alive now if she’d dialed down the quackery and gotten a physical now and then. She had self diagnosed some other problem, but I really wonder if it wasn’t the beginning of the cancer that killed her. My dad had a stroke, possibly because he relied on her quackery. (The BP meds made him tired. But there are alternatives if one becomes a squeaky wheel.) OTOH, my grandmother had surgery for cancer when there really wasn’t much hope for recovery.

    I’m sure there are some bad lab tests, and I’m sure that tank test had some huge failure of calibration or methodology. However, if you had another one or two from some entirely different organization, I’m guessing you’d get a far more realistic answer. I guess bone density issues might skew the results a bit, but not like this.

    BTW, the lab tests that the local hospital has seem remarkably consistent and usually make sense when compared to my weight and recent habits. But making a big decision on the basis of one or two lab tests is likely a mistake. (Okay, if they take an x-ray and they find a pair of forceps left over from that operation, one image probably does establish the problem with no doubt!)

  50. That test could have been done by a 5 year old. 16.9%??? That is the most ludicrous result ever.