When you go to a doctor, whether for a routine checkup or because of a specific concern, you will usually undergo a series of tests that will give values for a variety of biological markers. Your measures will then be compared with standard benchmarks to see if you fall outside the norm, and if you do, that will be perceived as a problem to be addressed. Implicit in this methodology is that there is a ‘universal patient’ whose biometric markers represent the norm that everyone should aspire to. But where do these norms come from? How valid are they? To what extent should they be used to diagnose and treat people?
When my older daughter was a baby, she was exceptionally chubby. But as she approached her first birthday, she rapidly became skinny, so much so that people had difficulty recognizing the infant in the photograph of her that was on the sideboard (taken at around six months) with the toddler now running around the house. In the regular doctor’s visits, her weight was always on the very low end of the standardized height-weight charts. But her pediatrician, who was an older man, did not seem concerned and so neither were we.
But as it came time for her to start elementary school, he warned us that teachers and nurses at her school might express to us alarm at her being so thin. He told us to ignore them, that she seemed perfectly healthy and well-adjusted. Sure enough, we heard from some people in the school that she was too thin and that it might be a cause for concern. But we ignored them because she seemed to be just a regular child. We did not go out of our way to ‘feed her up’, to get her to put on weight. But I know parents of young children who worry when their children do not fit into the norms and, conversely, there are even parents who subtly brag about how high their offsprings score on them.
In the March 31, 2025 issue of The New Yorker, Manvir Singh discusses the pernicious influence of these standardized measures because they simply do not capture the natural diversity of people across the globe.
In “Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us” (Avery), Herman Pontzer, an evolutionary anthropologist at Duke University, recounts facing a similar conundrum. While Pontzer was visiting a semidesert village in northern Kenya to study the Daasanach pastoralists, a German charity representative told him that the community was being devastated by malnutrition. Charity workers had plotted the heights and weights of Daasanach children on World Health Organization charts—the same ones our pediatrician used to monitor my daughter’s growth—and determined that more than two-thirds of the kids were malnourished. As a result, families were enrolled in a nutrition program and provided with high-calorie, industrially processed supplements. Yet, as with my daughter, the numbers didn’t align with ordinary observation.
“Everywhere we went, children were running, playing, and laughing,” Pontzer writes. “Kids being kids. They didn’t seem low on energy, nor did they seem particularly short, or ‘stunted.’ ” He saw no other signs of chronic starvation, such as bloated bellies or reduced fertility among adult women. The kids were slim, but in the lanky way typical of so many East African pastoralists.
When Pontzer and his team tracked the growth of Daasanach children, they uncovered patterns that sharply diverged from the W.H.O. curves. At around age two, these kids gain height at rates seldom seen elsewhere in the world. At five, they stand taller, on average, than well-fed kids in Europe and North America. At the same time, they put on weight more slowly, developing lean physiques that are optimal for heat dissipation. Where the German charity diagnosed deficiency, Pontzer saw adaptation.
The intent of the original growth charts was well-meaning, to provide a measure of health to countries and communities that were not able to do their own data collection and analyses. But the measures adopted by the WHO were originally based on the population of a single community in Yellow Springs, Ohio. But even after they broadened the data set in 2006 to include Oslo, Norway; Muscat, Oman; Pelotas, Brazil; New Delhi, India; Accra, Ghana; and Davis, California, that still was not sufficient to capture the diversity of populations. Only New Delhi was from Asia. Africa in particular has huge genetic diversity and yet only Accra was included. As a result, these charts raised different problems.
So charts meant to protect children’s health may be failing them across the globe, missing growth disorders in tall populations while pathologizing normal development in shorter ones. Parents in Mumbai, Manila, and Minneapolis alike must navigate a medical system built on standards that don’t reflect their children’s physiological realities. Some children who need care may be overlooked; others are subjected to unnecessary and potentially harmful interventions.
Another problem is with zinc and Vitamin D levels.
Criteria for zinc deficiency, as defined by the International Zinc Nutrition Consultative Group, are based on data collected in the United States between 1976 and 1980. Bear that in mind when you hear claims that more than a billion people are zinc-deficient. The threshold for Vitamin D deficiency is also based mostly on research involving Europeans and North Americans, leading to the claim that ninety per cent of Indians lack sufficient Vitamin D, despite the subcontinent’s abundant sunlight.
Like most South Asians, my blood tests invariably say that I am deficient in Vitamin D. I ignore the recommendations to take supplements. I suspect that my daughter’s pediatrician was not only older but old school, using his own observations and diagnostic skills to put the statistics in context. He must have observed that her mother was very petite and that her father would be underweight according to the BMI charts and yet we were healthy and so there was no reason to be alarmed that our daughter took after us. Decades later, she is still slim and tall, but fit and healthy and athletic.
Yes, norms are useful as indicators, but trying to coerce people to fit norms is insane.
Diversity is a thing! (At least until Trump erases it.)
This is a good blog post.
It has been estimated that 85% of Americans have some symptoms of metabolic syndrome, such as diabetes, pre-diabetes, high blood pressure, obesity, etc.
Yet standard ranges for blood tests and other medical tests are usually based upon a 2-sigma distribution about the mean. In other words, the “desirable” test results are defined by looking at the total population, and assuming that “most” people are healthy. Clearly, that might not always be a good assumption.
Further, there can be special cases. For example, indigenous peoples in Kenya were studied, especially the Massai and a neighboring tribe. These two tribes frequently intermarried, so genetically they were a unified population. But culturally, the Massai traditionally had a cow-based diet of meat, milk, and blood products. Meanwhile, their cousin tribe was largely vegetarian. The two tribes had different average physical properties. Any table of standards would need to specify if it was a table for one tribe or the other. Or were people trying to fit a single bell shaped curve over a two-humped camel of the data sets? Clearly, range data is only meaningful for the specific population category that it was collected for.
Similar tensions exist in many countries where a traditional diet and lifestyle diverged from the common Standard Western Diet etc.
For example, modern people in Okinawa eat similarly to most Americans. But the traditional Okinawa diet had pork, seafood, and some vegetables, but little processed junk food. So it is now meaningless to talk about Okinawa diet and health unless one specifies which population is being discussed.
Thanks for a great post.
People -- usually but not always fat people- complain about “standards” like BMI, as though all doctors apply such things blindly, like dumb automata running a prescriptive procedure, unwaveringly and without judgement.
Nice to see a worked example of what actually happens, which is that BMI *is* measured, then assessed professionally in context and advice given accordingly.
And if your doctor isn’t doing that, get another doctor.
Of course your doctor might do that, and give you advice you don’t like, at which point you could go get a medical degree of your own and then professionally disagree (if you still do disagree, once you have the knowledge), or just ignore them irrationally (which is much easier).
If you’re even slightly competent, norms are the place you *start*, not the place you stop. Its like the Ideal Gas Law -- you do the quick calc using that to get an idea what’s going on… But if you*know*the system is non-ideal, you keep going, into experiment or simulation. The existence of non-ideal mixtures doesn’t invalidate the use of the law, it just means there’s a bit more work to do.
Mano, I’m not sure on what grounds do you ignore the advice regarding vitamin D? In any case, especially at your age, you can have your bone density measured and know for sure where you are. I managed to mess my bones up by living in western Washington and not taking vitamin D for over 10 years. I have been supplementing for many years now, but the early damage remains. Also, vitamin D alone won’t help if one isn’t getting enough dietary calcium.
sonofrojblake, anyone complaining about BMI is invited to measure waist circumference to height ratio (should be less than 0.5) or waist circumference to hip circumference ratio (should be less than 0.9 for men, and less than 0.85 for women, though IME it is more difficult to get a reliable hip circumference measurement). And if they are still unhappy, there is a body roundedness index. I know people who are trying to develop a predictive index for ‘does the person being measured need to make a greater effort to lose weight’ based on metabolic measurements.
@3 sonofrojblake mentioned the Ideal Gas Law, and I thought, “Yep, and immediately that’s why we have steam tables. Most people think of water as a liquid and not as a gas. Even high school chemistry students should consider the existence of liquid nitrogen as a demonstration of non-ideal gas law behavior.
I find it hilarious that they chose Yellow Springs and Davis when trying to find universal norms. I grew up near the former and worked in the latter and neither of them strike me as typical populations.
This can also lead to problems if you are within the ‘normal’ range, as you may not be in the right place for you, say if you are at the bottom of the range and should be at the top to remain healthy. I have had this discussion with GPs several times over the years, after suggestions that the amount of levothyroxine I take should be reduced. My current GP practice do the tests, but also take into account how you are doing, and recently raised the amount I take. I suspect it should still be a little higher, but I am certainly doing better on the increased dose.
“Only New Delhi was from Asia.”
Actually, Muscat is also in Asia.
Not quite sure why sonofrojblake @3 has to pre-emptively blame “fat people” for ignoring “advice [they] don’t like”…
@9:
Except, y’know, I didn’t.
And you do know I didn’t, because you have to quote the words “fat people” from the first paragraph, then elide everything until the bit in the THIRD paragraph about ignoring advice, which was explicitly NOT addressed to “fat people” at all but in fact directly to the reader. That was why you had to delete the word “you” -- which was what I meant -- and replace it with the word “they” -- which is what you wanted me to mean, presumably. (Of course, you might consider yourself to be “fat people”, but I can’t know that and in any case the point would, obviously, be exactly the same if you were “thin people” ignoring medical advice, the point being “don’t ignore medical advice you don’t like”. YOU might think that applies only to fat people, but that’s not what I meant and it’s not what I said).
Full marks for effort and mental gymnastics to come up with the reading you did though, it certainly took some severe twisting to get to the interpretation you wanted.
Might be more productive to respond to what I actually write, though, rather than rearranging my words from entirely separate paragraphs until there’s something for you to be angry about.