When you may not wish to be “normal”

November 28th, 2009  |  Published in Stumpblog  |  20 Comments

Brad Pilon‘s published some recent data, drawn from a 2009 study in the American Journal of Clinical Nutrition, on the average body fat % of the general population.

Now, usually we say “Oh, average for a woman is around 21-25%” or some similar number.

Actually, the US female average is… wait for it… around 40-42%.

Yes, that means for the average American female, NEARLY HALF HER BODY IS FAT. Only 60% is everything else: skeleton, organs, muscles, whatever she ate for lunch, etc.

This is why, whenever I hear people say smugly, “Oh, body mass index doesn’t account for muscle,” I want to ask them if they are actually hard-training NFL athletes or bodybuilders, because 99% of the time, BMI actually does correlate fairly well with % body fat.

Sure, the individual numbers may be slightly off. Maybe you’re really 31.5% fat and not 32% or 30%. This study used DEXA to measure body fat, which is very accurate. You may never have access to this kind of precise measurement technique.

But if your BMI is way higher than it should be, and you’re not on steroids and in the gym every day, there’s an excellent chance that you’re probably carrying too much body fat. (And, in many cases, you’re still carrying too much fat even with the steroids and gym rattery. Have you seen some of those offseason bodybuilders?)

No, your skeleton is probably not “too dense”. No, you are probably not a rippling pile of woman-steak. If you’re way into the BMI red zone, if you’re not an elite hard-training athlete, and if you’re American, you may wish to reconsider your nutrition program.

40% is not health at any size. 40% is well out of the physiological range of your body’s ability to handle its bidness.

40% body fat means that your glucose metabolism is in big trouble; your destructive cytokines are running amok; your reproductive hormones are out of whack; your liver is redecorating its house with big steatotic globs of lipids; your arteries are landscaping with atherosclerotic plaques; your airway is compressed; your joints are screaming “Ouch!” and you’re a walking inflammatory state.

If you’re “normal”, you may want to think about how to become a weirdo. If you’re “normal”, and working on abnormality, kudos to you — keep up the good work!


  1. dana says:

    November 28th, 2009at 9:42 pm(#)

    Just to play devil’s advocate and out of genuine curiosity: what’s the solid reason for thinking that 40% is out of the physiological range for the body’s ability to handle its bidness? Does it account for age? I wonder in part because the chart given is a bell curve, not skewed at all; it would be strange in most cases if “normal” meant “in the bottom five % of body fat”, descriptively. So something normative must be meant by “normal”, and I’m wondering what the justification is for that. (Devil’s advocate thinking: if we’ve defined “normal” as 21% and only 2% of the population is there, maybe the problem is with the definition.)

  2. Mistress Krista says:

    November 29th, 2009at 9:00 am(#)

    There is a difference between numeric/statistical “normal” and physiological “normal”, of course — one problem is the terminology. I would define physiological normal as a range in which the body is able to properly execute its intended and required metabolic functions.

    To be devil’s advocate to the devil’s advocate, I would like to see data that demonstrates that someone with 40% body fat is physiologically normal by our standard indicators of optimal function, which include:

    -blood pressure
    -glucose metabolism
    -insulin sensitivity and function
    -liver function and presence/absence of steatosis
    -respiration (which includes proper resting sleep function)
    -blood triglycerides
    -functional mobility
    -pain index
    -performance of daily life tasks
    -reproductive hormone function, balance, and levels (including pregnancy)
    -inflammatory markers such as elevated inflammatory cytokines
    -development/presence of inflammatory sequelae such as autoimmune disorders, type 2 diabetes, heart disease, and cancer

    Note that none of these are “athletic” endeavours.

    If 40% body fat were not a problem, then we would expect to see quite healthy people in this range. We do not.

    All data we have to date indicates that people falling far out of the range we commonly take to be ideal (which, in my opinion, is a pretty broad range and probably broader than many authorities would allow) experience moderate to severe disruptions to many of these.

    Sure, maybe the tipping point into a disease state for one person (esp. if she’s apple-shaped) is 29%. Maybe the tipping point for someone else is 40%. It also depends on the distribution of body fat, but past a certain point (and by the way, this DOES include aging) you are most definitely gambling with physiological sub-optimal function.

  3. Mistress Krista says:

    November 29th, 2009at 9:06 am(#)

    And to answer your question about why the data distribution is a normal curve: I’d propose that what we are looking at is the manifestation of the body’s management of the conditions with which we’ve presented it. Body fat distribution has fairly little to do with individual choice in most people. It’s absolutely under our conscious control — no question, otherwise there wouldn’t be much point to this website — but for the average person, body fat levels are much more a function of the way in which our 200,000 year old genes combine with a 21st century North American environment.

    This normal distribution probably represents the ability of the body to self-regulate in a certain way given certain environmental conditions.

    In a prison camp you’d likely see a normal distribution that moved much farther to the left. In that case perhaps 18-20%, or even less, would be “normal”. (But again, not exactly physiologically ideal, for different reasons.)

  4. Varsha says:

    November 29th, 2009at 10:02 am(#)

    Disease is normal,eating trans-fat and sugar is normal,being perched on a chair for 16-18 hours is normal,always being propelled by automobiles is normal.The very act of doing anything by way of your health in this “normal” scenario makes you a weirdo.The problem certainly is with the definition of normal!

  5. dana says:

    November 29th, 2009at 10:15 am(#)

    I’m not up on the literature, and while the plural of anecdote isn’t data, I know that my mother’s body fat is around 36% (BMI around 25), she exercises (she needs to lift heavier things, but after decades of inactivity I’m happy she has a three-year-old gym habit), and she’s in excellent health, by whatever stats you want to grab.

    Now, she’s a sample of 1, and she could just have freakishly good genetics. But I was asking in good faith; and in part because I was genuinely surprised by the chart. 40%? 60% of the population with serious health related issues lurking or developing? Eek.

  6. Mistress Krista says:

    November 29th, 2009at 1:44 pm(#)

    Dana: Fitness and good nutrition does, to some degree, improve overall health markers, which is awesome. I would love nothing more than for ALL bodies to be active and well nourished. An inactive, poorly nourished 20% bf is a worse situation than a very active, well-nourished 28% — no question. Exercise improves things like glucose disposal and insulin sensitivity.

    However, past a certain point, the freebie runs out, especially as mechanisms become less robust with age. There is interesting research coming out now on the difficulties that many heavyweight athletes who carry a lot of body fat (e.g. NFL linebackers, superheavyweight classed strength athletes) are having with things like sleep apnea and metabolic syndrome. Despite their high level of activity and, I’d assume, reasonably decent nutrition (esp. at the pro level, where most variables of an athlete’s life tend to be controlled/monitored), the mechanical and metabolic load of a certain % of body fat cannot be compensated for — again, esp. as they get older.

    The problem with excess body fat is both mechanical and chemical. Mechanical b/c of loading and the space displaced by the tissue itself (e.g. around airways). Chemical because adipose tissue actively secretes hormones and chemical messengers.

    There are always one or two genetic superheroes who manage to smoke, drink, do XYZ risk factor, and remain healthy. At a population level, however, the risks certainly do manifest themselves.

    On the plus side, research also shows that along with activity and good nutrition, even slight reductions in body fat can have health advantages.

    There is also fascinating data that shows metabolic improvements immediately following bariatric surgery — like, immediately — before actual fat loss occurs. This tells us that there is some additional mechanism at work, likely to do with hormones secreted by the stomach, beyond the physiology of adipose tissue. (I’m not advocating bariatric surgery, I just think that’s really interesting.)

  7. Elizabeth says:

    November 29th, 2009at 9:06 pm(#)

    A while ago I wrote a defense of BMI which, in part, directed people to your “Honesty is the best policy” article. The main thrust was that yes, you are probably normal, and yes, that means BMI applies to you.

    I actually am what you’d call “big-boned” — large hands and feet, oversized head (and thick skull, I suspect) but I figure that gives me maybe five extra pounds on the BMI scale. Maybe. Not worth rejecting the entire concept for. And, while my muscles do appear to have considerable growth potential considering what they’ve done over the past year, I can still tell the difference between them and the nice juicy layer of fat over them.

    I think one problem people really have is the designation of 30+ BMI as “obese.” Colloquially, “obese” means “really super-fat,” like Mr. Creosote fat, and the average 30-35 BMI person will say “I’m not obese! Overweight, sure, but not obese!” If you say that obesity is the level of excess fat that starts affecting your health, though, and you ask these people if they have high blood pressure, high cholesterol, pre-diabetic indicators, shortness of breath after exercise, or joint pain, well… it looks different all of a sudden.

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  9. alison says:

    November 30th, 2009at 8:33 am(#)

    Ah Krista, I think I love you for this article.

  10. Cassandra Forsythe says:

    November 30th, 2009at 12:24 pm(#)

    Wow. Just for curiousity sakes, I pulled up the full text of this paper just to check the finer details.

    What I found interesting is that the investigators stratified women by BMI and age and then reported their body fat percetage (because in this original analysis, all 6,000+ women aged 20 to 80 of different ethnicities and BMIs were included as this 40% average).

    Women with a BMI <25 and in the age range of 20 to 39 (Still, kind of a large range if you ask me) had an average body fat of 32%. Women who were white, non-hispanic with a BMI 35 – they had 48% body fat.

    Still, all of this is very disturbing and supports the observation that Americans are becoming very over-fat. And, as Krista pointed out, there are very few health benefits of higher body fat %.

    For those that have never had a DEXA body comp scan done, don’t compare your results with another method to the results here. DEXA compared to most other methods, usually reports higher body fat percentages – but this really depends on the measurement used in comparison. For example, a hand-held BIA will give you a different body fat just based on your age – try it, put a higher age than you actually are when using it and watch your body fat magically increase.

  11. Lau says:

    November 30th, 2009at 1:44 pm(#)

    What is the “normal” correlation between body fat and BMI? I’m one of those definitely-overweight-by-BMI women who insists that I’m OK. I’m 5′ tall and 130-135 lbs usually. I have a scale that’s supposed to measure body fat, but it fluctuates between 17-22% within a day so I doubt it’s accuracy.

    My cholesterol, blood pressure, etc. are fine. The only functional problem I have is an artificial knee, from bone cancer, not from ruining my joints because of my extra weight. Ironically the only time as an adult that I have been a “healthy” weight in terms of BMI was during chemo.

  12. Mistress Krista says:

    November 30th, 2009at 2:20 pm(#)

    Lau, at 5′ and 135 you are still in a healthy range if you are active and well nourished. When we’re talking risk, we’re not talking about 10-20 lbs extra. To get to 40% body fat requires significant additional adiposity.

    BMI is fairly closely correlated with body fat %, although researchers recognize that there are individual differences that are statistically significant but not “real world significant” at the end ranges (i.e. the very lean and very obese). There is some fluctuation with age but not so much among adults — more between adults and children.

    Complaints about the BMI being used as a blunt instrument should really be directed at media, insurance companies (in the US), and other similar oversimplifications. All physiology researchers know that BMI is at best a “best-fit” predictive model, and like all predictive models it is subject to some range of error.

  13. Mistress Krista says:

    November 30th, 2009at 2:25 pm(#)

    Cassandra’s point is very insightful. In the US there are major, major differences in the manifestation of obesity and overweight, and these correlate very closely with ethnicity and income. Nearly 100% of black women in the lowest income bracket in the US are overweight, whereas a much smaller proportion of middle-class white women are. This is another clue that obesity is mostly about environment, socioeconomic structures, and access to health resources.

    That being said, many folks of Hispanic descent carry genes that make them more susceptible to the metabolic foundation for obesity, such as poor glucose tolerance and central adiposity (fat around the middle — the apple shape). This is also true for some indigenous groups, esp. those in the US Southwest.

  14. Lex says:

    December 1st, 2009at 6:21 am(#)

    I just checked out the ‘BMI Project’ over at a fat acceptance blog and coming over here to read this makes me feel better. I like your point about non-hard training athletes saying BMI doesn’t account for muscle. The first thing I thought of when I saw the pictures on the ‘BMI Project’ was that, well, most of them look like they fit their ranges well. There were a few exceptions and one of them stood out to me because she looks fit but is classed as overweight. I know several women who fit that description and it really isn’t that strange when you know their fat percentage as well. For the rest of them, it looks like BMI is a good gauge. The ‘project’ would have made more of a point if more information was given, like fat percentage for a start.

  15. Lyn says:

    December 1st, 2009at 8:30 pm(#)

    I sought solace in the BMI project a couple of years back when I was still in denial about my diagnosis of pre-diabetes. I think it boils down just to what Elizabeth says: that the popular image of “obese” is a size that would appear on peopleofwalmart.com. As Lex says, that people look reasonably healthy with a BMI over 30 doesn’t prove anything about what might be happening to health markers, especially as people get older. Here the post on metabolic syndrome is relevant as well. Let’s face it: Type 2 Diabetes is not a social construction.

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  17. sandy peters says:

    December 10th, 2009at 7:47 pm(#)

    What I find interesting is that I’ve recently gained 25 pounds (since I quit marathon training after an injury). I complain about how I’m just huge now, and my children are constantly telling me that I shouldn’t worry about it because now I look normal. I’m finally average, and I should just be happy. Yes, I wasn’t even on the BMI chart for awhile there when seriously training, but even being in the middle of the “normal” BMI now, is so much larger than I’ve ever been (unless pregnant–and I’ve had 5 kids) that I’m thinking the charts are actually very, very generous. I’m in the middle of my BMI and I need to face it; I have a serious muffin-top now. Why does everyone else tell me to be happy I’m now average? Since when was being average a goal?

  18. Sue says:

    December 21st, 2009at 10:44 am(#)

    Bin Laden doesn’t need to work on killing Americans, McDonald’s is doing the job for him. It is now considered normal to eat several cans of soda, fried foods, enriched bread and cheese. You are a freak if you eat whole grains and anything green.

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    January 27th, 2010at 4:58 pm(#)

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  20. ovpemar says:

    December 15th, 2010at 10:51 pm(#)

    “When we’re talking risk, we’re not talking about 10-20 lbs extra. To get to 40% body fat requires significant additional adiposity.”
    What I can not believe!

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