Shortcomings of the Body Mass Index (BMI)

I have been meaning to write about this topic for a while, and now I have Nancy Pelosi and Donald Trump to thank for spurring me to doing so. In case you missed it (or you’ve forgotten because the news moves so quickly), last week Pelosi said that she would rather Trump refrain from taking hydroxychloroquine as a prophylactic against COVID-19, which he had been doing for more than a week. Pelosi’s comments revolved around the lack of scientific evidence of the drug’s efficacy, and that fact that it appears to be harmful. Her apparent concern was followed by some not very subtle backhanded comments, adding that Trump was at heightened risk for drug complications due to: “his age group and in his, shall we say, weight group – morbidly obese, they say. So, I think it’s not a good idea.”

Weight is a sensitive topic. Pelosi’s comments were seen by some as justified comeuppance, since Trump has an expansive history of insulting people, but they were more widely panned as fat-shaming. Still others, such as CNN Political reporter Chris Cillizza, wondered whether Trump really was in fact “morbidly obese” by looking at CDC guidelines on the body mass index (BMI).

There are certainly more important things going on in the world right now than worrying about weight or BMI. Still, there is some evidence that people in higher-income countries under lockdown are gaining weight – the so-called “quarantine 15” – while people in lower-income countries are at higher risk for famine. As someone who has used BMI in research, I’d like to focus on its uses and some of its shortcomings, as well as the potential stigmatizing effects of labeling people by BMI categories.

BMI is used by an array of health professionals – physicians, nutritionists, epidemiologists, humanitarian aid workers – as a screening tool for people who might be under- or over-weight, as a warning for potential health problems. One of the reasons BMI is so widely used is its simplicity. All you need are two measurements: height (in meters) and weight (in kilograms), which are then plugged into the formula kg/ m2. And, unlike other more direct ways of assessing body composition, such as skinfolds, dual-energy x-ray absorptiometry, or underwater weighing, BMI can be ascertained with just a scale and a stadiometer. This makes BMI a cheap method that requires minimal training. This also makes BMI a portable, field-friendly method for researchers (including biological anthropologists) working with people who live in a range of environments.

Categorizing People by BMI

A higher BMI is suggestive of higher body fat, which is a risk factor for various morbidities including type 2 diabetes and cardiovascular diseases. For that reason, health organizations such as the CDC use rough categories to ascertain who might be at risk for elevated body fat (or adiposity). In adults, “absolute” cutoffs for categorizing adults are recommended:

  • Underweight – below 18.5 kg/m2
  • Normal or healthy – 18.5 to 24.9 kg/m2
  • Overweight – 25.0 to 29.9 kg/m2
  • Obese – 30 kg/m2 or higher
    • Class 1 Obesity – 30 to 34.9 kg/m
    • Class 2 Obesity – 35 to 39.9 kg/m
    • Class 3 Obesity – 40 kg/m2

If you know your height and weight, there are simple ways of finding your BMI if you don’t have a calculator handy, such as this site. Or, you may have seen a chart like this before.

Continue reading

On Multiraciality: Perceptions of Homogeneity and Difference

“I note the obvious differences between each sort and type./ But we are more alike, my friends, than we are unalike.”  (Maya Angelou, Human Family)

.

It’s been said that young primates engage in social learning in three main ways (van Schaik 2016). They can obtain information horizontally (from peers), vertically (from parents), and obliquely (from other adults). For the most part, the vertical transmission of information tends to flow in one direction; juveniles learn from the experiences of their parents rather than vice versa.

Yet parents can also learn from their kids. The street is not entirely one-way. My own children (who are also primates, just like you and I) have taught me a lot: from what they learn in school, see online, or their slang (derp). As “biracial” children, they’ve also taught me a few things simply by existing. There are general lessons that most parents learn – that having children can reorient priorities, and that parenting is a mix of vicarious pain, joy, and fear. For me, one specific lesson as a specific parent of these specific children, has to do with the ways that people perceive similarities and differences. I’ve been hesitant to write about my kids here (we all deserve some privacy). Still, I think there are some lessons I’ve learned that might be useful.

First, a step back. Most of my recent ancestors, as far as I know, come from Ireland and Britain, with some Scandinavians thrown in there, as well as ancestors from other regions of Europe. Oh, and Neanderthals too; they aren’t exactly recent, but we can’t forget them. Before that, my ancestors eventually trace back to Africa, as is true of everyone. If someone were to ask me about my ethnicity, I’d probably say that I am Irish-American, though I know that any label must necessarily discard some complexity. After all, a single name cannot possible encompass the nearly infinite number of  ancestors standing behind me. Identity, ancestry, and genes certainly correlate with each other, but never perfectly so. My wife is the daughter of Korean immigrants and would refer to herself as Korean-American. And her recent family tree, as far as she knows, contains ancestors who lived not only in Korea, but also in northern China.

With the kids at the beach.

Continue reading

“I’ve never seen a Chinese monkey” (Essentialism & Human Variation)

I taught my first undergraduate anthropology class seventeen years ago, which is sometimes hard for me to believe. In that time, I’ve had over two thousand students enrolled in my courses, many of whom have left an impression on me. I hope I make a good impression on them too, though sometimes I have my doubts. A few years ago, a student asked me what my name was as they started to fill out the line after “Instructor” on the front page of their exam blue book. That was about halfway into the semester. You can’t reach them all, I suppose.

During my fourth year of teaching “Introduction to Biological Anthropology,” we got about two-thirds into the semester, and I paused to take the class’ pulse on how things were going. I asked them if they had any general thoughts about the class, such as what ideas they found interesting (or not), things they wished we could discussed more in depth, etc. I have since forgotten most of the students’ comments, except for one.

I remember that he wasn’t exactly the best student, and that he had struggled with most of the graded assignments. Nonetheless, I still learned something from him that day. He told the class that he thought evolution was an interesting idea, but he was skeptical about it applying to humans because, as he said, “Well, I’ve never seen a Chinese monkey.” This all occurred a long time ago, but I remember that at first I was puzzled by what he meant. And then it clicked.

Continue reading

The Ecosphere of Kindness

From Andrew Solomon:

“And there are people who think that the existence of my family somehow undermines or weakens or damages their family. And there are people who think that families like mine shouldn’t be allowed to exist. And I don’t accept subtractive models of love, only additive ones. And I believe that in the same way that we need species diversity to ensure that the planet can go on, so we need this diversity of affection and diversity of family in order to strengthen the ecosphere of kindness.”

“The Fundamental Connection That We All Share”

On his visit to Ethiopia, U.S. President Barack Obama viewed the fossil remains of three famous human ancestors. These included two belonging to the 3 to 3.8 million-year old hominin species Australopithecus afarensis, “Lucy” and “Selam”), as well as “Ardi” from an older species Ardipithecus ramidus. (Click here for a nice overview of our hominin family tree). Later, he said this

“When you see our ancestor, 3.5 million years old, we are reminded that Ethiopians, Americans, all the people of the world are part of the same human family, the same chain… And as one of the professors (Zeresenay Alemseged) who was describing the artifacts correctly pointed out, so much of the hardship and conflict and sadness and violence that occurs around the world is because we forget that fact.  We look at superficial differences as opposed to seeing the fundamental connection that we all share.

I think Obama got it right, which isn’t surprising, since his mother was an anthropologist. Humans everywhere belong to the same species and share common ancestry. We have our differences — some trivial, some significant to us — but our bedrock should be that shared connection. That may be an ideological approach, but the nice thing is that it’s also scientifically accurate. 

Pesident Obama touches the fossilized vertebra of Lucy, an early human ancestor in Ethiopia on Monday. Photograph: Jonathan Ernst/Reuters

President Obama touches the fossilized vertebra of Lucy, an early human ancestor in Ethiopia on Monday. Photograph: Jonathan Ernst/Reuters

Nicholas Winton & “The Only Way Out”

“And you think it’s easier
To know your own tricks
Well, it’s the hardest thing you’ll ever do.”

 

On my drive into work this morning, I caught the latter half of an interview with Nicholas Winton, the “British Oskar Schindler,” who helped rescue over six hundred Jewish children from Nazi-occupied Czechoslovakia just before World War 2. Recognizing the impending danger, Winton helped coordinate a number of trains to get the children to Britain, where families had volunteered to take them in. He was later reunited with some of those children – since grown – in 1988, recorded by the BBC. It is a very moving scene, particularly considering that the last train carrying children did not make it, and all of its evacuees were believed to have died in concentration camps. 

 

Winton is now 105 years old, and the interviewer asked him a range of questions about his role in the evacuations, his view of himself as a hero (he wanted no part of this), and his thoughts on the changes in the world that he had seen over his very long life. Overall, he said, he was pessimistic about the way the world has changed. We’ve grown more efficient at killing each other, and seem mired in conflict and unable to get out of our own way. 

The key, or “the only way out,” as he put it, is finding commonality with each other through ‘ethics.’ As a child, he embraced his own Jewish heritage, but then converted to Christianity. Later, he grew disillusioned with religion altogether when he learned that religious figures on both sides of World War 2 were praying for their own countries to win. I wanted to quote his exact words, so I found this print version of the interview. 

Continue reading

Developmental Plasticity and the “Hard-Wired” Problem

“Development is the missing link between genotype and phenotype, a place too often occupied by metaphors in the past … But a strong emphasis on the genome means that environmental influence is systematically ignored. If you begin with DNA and view development as “hard-wired,” you overlook the flexible phenotype and the causes of its variation that are the mainsprings of adaptive evolution.” (Mary Jane West-Eberhard, 2003: 89-90)

“Genes, unlike gods, are conditional. They are exquisitely good at simple if-then logic: if in a certain environment, then develop in a certain way… So here is the first moral of the tale: Don’t be frightened of genes. They are not gods; they are cogs. (Matt Ridley, 2003: 250)

 

Plasticity: actor Christian Bale at two points in time. Same genes, different phenotypes.

Plasticity: actor Christian Bale at two points in time. Same genes, different phenotypes.

In his book The Triple Helix, Richard Lewontin told the story of the molecular biologist and Nobel laureate Sydney Brenner, who – while speaking at a conference – predicted that one day we would be able to “compute” an organism (2002). All we would need are two things: the organism’s full genome and powerful enough computers that were up to the task.

The idea is seductive. Genes are sometimes seen as self-sufficient molecules, almost existing in a vacuum, that contain all the information necessary to code for proteins. From there, it’s not a very big logical leap to think that if you had the genome, you could enter the code in some database, hit “run,” and then watch some digitized version of the organism unfold.

In fact, scientists are doing something much like this for the tiny roundworm C. elegans with the project OpenWorm. Yet even for a relatively simple organism such as this, with only about a thousand cells in total, there are reasons to be cautious. As The Economist warned in its write-up of OpenWorm: “Attempting to simulate everything faithfully would bring even a supercomputer to its knees.” However, this isn’t due solely to the limits of computing power (what if we had a super-duper computer!?). Rather, it’s a matter of how the question is framed.

Continue reading

Kindness and Regrets

Be excellent to each other.” – Bill and Ted (20th century philosophers)

 

From a commencement speech by George Saunders: 

“What I regret most in my life are failures of kindnessThose moments when another human being was there, in front of me, suffering, and I responded…sensibly.  Reservedly.  Mildly.”

Saunders then describes a memory from the seventh grade, when he did not defend the new girl in school who was teased for being different. Forty-two years later, he still thinks of her occasionally, and even though he was not personally cruel toward her, he regrets not going out of his way to extend her kindness. He then questions why kindness is often lacking, and he looks for prescriptions to make it more common.

The speech is a good one, and it stirred up some personal memories of instances when I could have used some kindness from someone. Sometimes it came; others it didn’t. There were also situations that called for me to be the one to extend kindness to someone else who needed it. Sometimes I stepped up, although probably not as consistently as I should have. Fear can be a powerful deterrent. Like Saunders, I regret those missed opportunities.

Of course, the opposite of kindness is cruelty, and I’m often distressed by the latest story of human callousness, where someone is belittled for not conforming to another’s standards. For those of us who are not Rhodes Scholar Olympians (which is to say, nearly everyone), we all fall short of socially constructed ideals in some way. Either we’re not attractive enough, or not stylish, athletic, or smart enough (or too smart). Too red. Too blue. Too promiscuous or too chaste. Too tall. Too short. Too neurally atypical. Or, we’re the ‘wrong’ weight, gender, race, sexuality, ethnicity, social class, or speak the wrong dialect. We can be incredibly creative at finding the holes in the armor to bring someone down.

For such an intensely social species, we often seem to go out of our way to make each other want to leave the group.

Continue reading

Empathy in Flux, Part 2

Jason De Caro recently shared this video from the Cleveland Clinic. For those who can’t watch it, the video shows various individuals in a hospital setting , with captions describing the most recent, pertinent events in that person’s life (a woman visiting her terminally ill husband, someone learns they’re about to become a parent, etc.)

 

I thought it was a nice reminder that external appearances are often superficial. All people have a complex history behind them, beyond just the snippets and cross-sections that we observe, particularly when meeting someone for the first time. In another post, titled “Empathy in Flux,” I wrote that single slices of a person’s life are never enough to fully understand the complexity of a person:

as Forrest Gump famously put it: “stupid is as stupid does.” I think this is an often misunderstood piece of folk wisdom. My interpretation of this is that one can evaluate actions without leaping to evaluations of states of being. Certainly one can do stupid things without “being” stupid. To believe another person “is” stupid (or any personality trait you can imagine) is to claim one has found the signal among the noise, while ignoring a LOT of complexity, the deviation around the mean. In short, we have just a cross-section in the totality of that person’s life. Even Hitler laughed. Even Gandhi had periods of depression. Certainly, we have more than a snapshot of these particular individuals’ lives, but we don’t have that for everyone we meet. How different would our impression of others be if we had that longitudinal data in front of us? Of course, for most people the amplitude of one’s personality does not fluctuate that widely. Most people are consistent in either being kind, or funny, or complete assholes. But context and variation are essential. 

Like all reminders to be mindful, the video is welcome (and necessary).

.

 

Human Nature, Humility, & Homosexuality

And, in the end, the love you take is equal to the love you make.” -Lennon/McCartney

Is that true?” – Chris Farley

….

.

Steve Silberman pointed his Twitter followers to a piece in Salon about the biography of Maggie Gallagher, the point person for fighting against same-sex marriage in the United States. Toward the end of the article, it quotes Gallagher on her views on homosexuality, same-sex marriage, and human nature, where she makes an analogy to Communism:

“One of the lessons I learned as a young woman from the collapse of Communism is this: Trying to build a society around a fundamental lie about human nature can be done, for a while, with intense energy (and often at great cost); but it cannot hold.”

The author of the article, Mark Oppenheimer, then writes this about Gallagher:

Same-sex marriage is just a big lie, she believes, like Communism.  It is weak at its foundations, like the Iron Curtain. It may get built, she seems to concede — in 10 years, or 20, there may be more states that recognize same-sex marriage, more shiny, happy couples raising rosy-cheeked, well-adjusted children, children who play with dogs and go to school and fall from jungle gyms and break their arms, children often adopted after being abandoned by the heterosexuals who did not want them or could not care for them — but in time (big time, geological time, God time) the curtain will be pulled back, or it will fall. Because it has to. It cannot be otherwise.” 

. Continue reading