Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
23 Dec

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.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I guess I’m 25% body fat then…

    Sterling wrote on December 23rd, 2009
  2. 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.

    primalman wrote on December 23rd, 2009
  3. 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.

    Gordon wrote on December 23rd, 2009
  4. 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.

    Dave wrote on December 23rd, 2009
  5. 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?

    mike wrote on December 23rd, 2009
  6. 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.

    Dave, RN wrote on December 23rd, 2009
    • 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%!

      hypnotikk wrote on December 23rd, 2009
    • 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.

      Uncephalized wrote on July 15th, 2010
  7. 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.

    Greg Carver wrote on December 23rd, 2009
    • If you cannot rely on their accuracy how can they be of value?

      Gordon wrote on December 23rd, 2009
      • Internal vs external reliability.

        AlyieCat wrote on December 23rd, 2009
      • As long as it’s consistent with its inaccuracy – ALWAYS measuring 4% too high, for example – you can still use it as a guideline.

        Aaron Fraser wrote on December 23rd, 2009
      • @Gordon,

        Greg said they’re valuable “directionally.” Which I agree. I use these tools to see the trend in bodyfat changes.

        Johnny at The Lean Saloon wrote on December 23rd, 2009
  8. 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! :)

    Cynthia wrote on December 23rd, 2009
  9. Use the mirror 😀

    arthurb999 wrote on December 23rd, 2009
  10. 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!!

    Kishore wrote on December 23rd, 2009
    • LOL on your comment – funny! :)

      BestSelf wrote on December 23rd, 2009
    • Good one!! 😉

      iisierra wrote on December 23rd, 2009
  11. 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!

    Jeff P (P stands for Primal!) wrote on December 23rd, 2009
  12. Another case in point:

    The blood test for celiac disease.

    jeff wrote on December 23rd, 2009
    • 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.

      Icarus wrote on December 27th, 2009
      • Plus, you know, it doesn’t really matter if you have celiac if you don’t eat grains anyway!

        Uncephalized wrote on July 15th, 2010
  13. Very interesting! Did the test use your age in any part of the calculations?

    Ray wrote on December 23rd, 2009
  14. 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.

    Mark wrote on December 23rd, 2009
    • 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.

      Gordon wrote on December 23rd, 2009
      • 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.

        Ben wrote on December 23rd, 2009
  15. 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?


    Frank wrote on December 23rd, 2009
  16. Astonishing!

    Jim Purdy wrote on December 23rd, 2009
  17. 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.

    Christian wrote on December 23rd, 2009
  18. 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.

    Christian wrote on December 23rd, 2009
  19. 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.

    Colleen wrote on December 23rd, 2009
  20. Ok now i’m depressed, i must be then 28%

    Mary wrote on December 23rd, 2009
  21. 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 😉

    Grok wrote on December 23rd, 2009
  22. 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.


    Brad Reid wrote on December 23rd, 2009
  23. 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.

    Alex wrote on December 23rd, 2009
  24. 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.

    fixed gear wrote on December 23rd, 2009
    • 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.

      Elizabeth @ The Nourished Life wrote on December 23rd, 2009
  25. 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.

    dr. pierre debs wrote on December 23rd, 2009
    • 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.

      Icarus wrote on December 27th, 2009
  26. 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.

    Hilary wrote on December 23rd, 2009
  27. Hmmmm … well then that may put me at about 110% BF.

    Roberto wrote on December 23rd, 2009
  28. 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.

    Ted Durant wrote on December 23rd, 2009
  29. 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.

    Christian wrote on December 23rd, 2009
  30. 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!

    Gina wrote on December 23rd, 2009
  31. 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.

    Mike Prevost wrote on December 23rd, 2009
  32. 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?

    Dave wrote on December 23rd, 2009
  33. 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.

    Licarrit wrote on December 24th, 2009
  34. 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.

    David Marcon, DC wrote on December 24th, 2009
  35. 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.

    mike wrote on December 24th, 2009
  36. 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%).

    anne wrote on December 24th, 2009
  37. 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?

    LittleNappingLion wrote on December 24th, 2009
  38. 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.

    Richard Nikoley wrote on December 24th, 2009
  39. 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. 😉

    Judymac wrote on December 24th, 2009

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