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BMI is trivial to measure conclusively, using tools that are almost universally available and ready. And at population scale, it's proven to be a strong and pre

BMI is trivial to measure conclusively, using tools that are almost universally available and ready. And at population scale, it's proven to be a strong and pretty signal for analyzing in studies like these as the ways in which BMI can fail for individuals is too uncommon for it to matter to population studies. It's a perfect tool to use for studies like these, as it can contribute understanding society-level concerns about the obesity epidemic and what impact we can expect it to have if it continues not to be tackled. But like with almost all medical and nutritional research, drawing conclusions for yourself as an individual based on these population-scale studies is inevitably fraught. In the case of BMI studies, you can often get a fair sense of whether you should be concerned or not, but do need to take into account other things that you know about your lifestyle and health. Your doctor, presumably, does exactly that. Meanwhile, body fat percentage tends to be very hard to measure accurately in the first place and has different techniques that tend to have different error characteristics, making it hard to correlate it between studies done through different clinics, let alone against someone's personal assessment at home or with their personal doctor/trainer/whatever. It probably has high relevance to some medical and nutritional outcomes, but isn't a very useful input variable for research because its inescapably noisy.

hirvi74 2y ago
I apologize if this is tangential, but I have noticed BMI research is often heavily criticized, but the same issues that plague BMI can easily be applied to psychometric measurements of intelligence (IQ), but somehow IQ is spared the same beating for some reason I must not understand. Perhaps my low IQ is showing, but why is one metric heavily criticized while the other is not? (Rhetorical)
- TylerE 2y ago
  Huh? I haven’t seen “IQ” seriously used in decades. Its flaw are well known.
  - hughesjj 2y ago
    Even in popsci/social media I've seen more and more awareness that it's "bunk" science. It's in the same category as all that "alpha male" theory, Meyers Briggs, polygraphs, and "left vs right brained" people. I'm starting to see more awareness around the concerns of "ballistic forensics" too, which is heartening.
    - hirvi74 2y ago
      > Even in popsci/social media I've seen more and more awareness that it's "bunk" science. Devil's Advocate: Then why is it so heavily used still? (Then again, I guess back to my initial point -- the same could be said for BMI.)
      - TylerE 2y ago
        Proof that's it's still heavily used in serious scientific literature?
        hirvi74 2y ago
        How do you define 'serious scientific literature?' In other words, what type of evidence would you like me to present? Does any peer reviewed research that uses IQ as a factor count as serious? (Obviously, I won't present research that is about IQ measurement.)
      - mewpmewp2 2y ago
        I have never had IQ test taken, but countless of times BMI has been calculated. Mind you I have had other mental tests done due to ADHD and Autism concerns, and some of them were similar about abstract logic, but they were combined with other things like focus, memory, multitasking, literary understanding and other mental capabilities. The results of these tests were presented as percentiles in the population.
        hirvi74 2y ago
        Interesting. I was given an IQ test for ADHD diagnostic purposes. There were other test given, as well. And in my opinion, the other tests were more indicative than the IQ test was (which I think is falling out of favor with ADHD testing). Then again, there were some issues with my test and scoring, so it makes me even more dubious of the (psuedo)science. I went through the arduous process merely for the formal documentation, which in hindsight has served me well. Not a single doctor has ever questioned my diagnosis. However, as the psych told me, a 10 minute conversation with me should honestly have been evidence enough. ;)
- swatcoder 2y ago
  > somehow IQ is spared the same beating I think this is the part you're getting wrong, which is why you're confused. IQ was contentious from its introduction in the beginning of the 20th century, caught some traction in the mid-century, and has mostly been on a decline of esteem and respect again since. It's never been very broadly accepted, let alone spared from criticism, nor have most other psychometrics, although (as always) there are bubbles of academia, industry, and the general population that swear by them and work to legitimize them. Kurt Danziger has published really great histories of all this. I'll add that his books are especially interesting in the context of all the AI buzz as insight into the history of "intelligence" (the word, the socially constructed concept, etc) helps wrap one's head around what it means when people working in CS try to repurpose its terminology in their own field.
  - tptacek 2y ago
    IQ is as far as I can tell quite well accepted as a diagnostic tool. The pushback is in its application across whole populations.
    - hirvi74 2y ago
      FWIW, anecdotal data is also considered a valid diagnostic tool too, and we know how unreliable such information can be. Also, by populations, do you mean groups of particular types of people or just groups of people in general? If anything, I thought IQ really only had anything close to merit at large population levels. Much of what I have read clearly fails at an individual level. However, if you are talking about IQ's application in regards to populations like one race vs. another, then yes, I think the pushback is well deserved.
      - tptacek 2y ago
        I agree with you about your last statement! I think it's actually a pretty interesting comparable to BMI. BMI: useful epidemiologically, across large populations, but much less useful individually. IQ: much less useful across large populations, but useful as a diagnostic/clinical tool in individual settings.
- hluska 2y ago
  IQ routinely gets destroyed. As an example, I was an undergraduate in the 1990s. My statistics class skewered the use of IQ back then. According to some friends with undergraduates, they still use that as an example of statistics being used badly.
  - hirvi74 2y ago
    People say that, but then people like me are administered the tests for clinical diagnostic purposes (right or wrong), and even my state still considers the scores to be a valid measurement of intelligence, and thus a factor in whether someone convicted of murder is eligible for the death penalty. I think the concept is bullshit myself, but regardless the damage is done, and still being done for what it is worth.
    - Izkata 2y ago
      My crude understanding is, we don't have a good way to calibrate above-average scores, but it is a good measure for below average (provided there aren't arbitrary barriers like the language it's in).
    - hluska 2y ago
      That’s too bad, but I replied to something that claimed there is no criticism of IQ. IQ is criticized and used. Those are not exclusive states.
      - hughesjj 2y ago
        Yup. Polygraphs are still used in the intelligence community and court too. I'm seeing the tide turn (imo), but by no means am I claiming it's no longer used (regardless of merit). I acknowledge I'm starting a personal anecdote which is subject to my own biases such as cohort affects.
  - Natsu 2y ago
    IQ is an interesting one. There are indeed plenty of issues in actually measuring it and deciding what we're even measuring to begin with, but at the same time, I've heard some people try to say it doesn't even exist at all. Which seems odd, because I've yet to see anyone who doesn't believe that stupidity exists and it's the other side of the same coin.
- buzzardbait 2y ago
  IQ is definitely not spared. It doesn't take a Mensa member to realize that human intelligence cannot be reduced to a single number.
worik 2y ago
> BMI is trivial to measure conclusively That does not make BMI a good measure.
- tptacek 2y ago
  It does for some applications, and not for others. In epidemiology you're looking at the number across broad populations, where a lot of the "three dimensions" idiosyncrasies cancel out. You're likely to run into trouble taking literal BMI constants and turning them into individualized patient care instructions, though.
  - nottorp 2y ago
    Or basically: there are outliers, and those tend to complain. But the average billions cancel them out statistically. I'm an outlier myself, and so is anyone who did some serious sports for a significant amount of time. There are other reasons to be an outlier too. But they're not so statistically significant.
    - xarope 2y ago
      ditto. Always a bit frustrating when the sadly overweight nurse looks at my height and weight, charts it, and mutters to themselves "borderline". My last visit, at least the doctor deigned to actually eyeball me and said "you look like you are quite active, we can ignore this".
      - nottorp 2y ago
        Oh I'm inarguably overweight, but not to the point the BMI would indicate, considering that when i was younger and in top form i was between 29 and 30.
  - worik 2y ago
    You are saying it is a not dreadful statistical measure. That is doubtful, but possible It is used for individuals. That is where it is harmful

hirvi74 2y ago

I apologize if this is tangential, but I have noticed BMI research is often heavily criticized, but the same issues that plague BMI can easily be applied to psychometric measurements of intelligence (IQ), but somehow IQ is spared the same beating for some reason I must not understand. Perhaps my low IQ is showing, but why is one metric heavily criticized while the other is not? (Rhetorical)

TylerE 2y ago
Huh? I haven’t seen “IQ” seriously used in decades. Its flaw are well known.
- hughesjj 2y ago
  Even in popsci/social media I've seen more and more awareness that it's "bunk" science. It's in the same category as all that "alpha male" theory, Meyers Briggs, polygraphs, and "left vs right brained" people. I'm starting to see more awareness around the concerns of "ballistic forensics" too, which is heartening.
  - hirvi74 2y ago
    > Even in popsci/social media I've seen more and more awareness that it's "bunk" science. Devil's Advocate: Then why is it so heavily used still? (Then again, I guess back to my initial point -- the same could be said for BMI.)
    - TylerE 2y ago
      Proof that's it's still heavily used in serious scientific literature?
      - hirvi74 2y ago
        How do you define 'serious scientific literature?' In other words, what type of evidence would you like me to present? Does any peer reviewed research that uses IQ as a factor count as serious? (Obviously, I won't present research that is about IQ measurement.)
    - mewpmewp2 2y ago
      I have never had IQ test taken, but countless of times BMI has been calculated. Mind you I have had other mental tests done due to ADHD and Autism concerns, and some of them were similar about abstract logic, but they were combined with other things like focus, memory, multitasking, literary understanding and other mental capabilities. The results of these tests were presented as percentiles in the population.
      - hirvi74 2y ago
        Interesting. I was given an IQ test for ADHD diagnostic purposes. There were other test given, as well. And in my opinion, the other tests were more indicative than the IQ test was (which I think is falling out of favor with ADHD testing). Then again, there were some issues with my test and scoring, so it makes me even more dubious of the (psuedo)science. I went through the arduous process merely for the formal documentation, which in hindsight has served me well. Not a single doctor has ever questioned my diagnosis. However, as the psych told me, a 10 minute conversation with me should honestly have been evidence enough. ;)
swatcoder 2y ago
> somehow IQ is spared the same beating I think this is the part you're getting wrong, which is why you're confused. IQ was contentious from its introduction in the beginning of the 20th century, caught some traction in the mid-century, and has mostly been on a decline of esteem and respect again since. It's never been very broadly accepted, let alone spared from criticism, nor have most other psychometrics, although (as always) there are bubbles of academia, industry, and the general population that swear by them and work to legitimize them. Kurt Danziger has published really great histories of all this. I'll add that his books are especially interesting in the context of all the AI buzz as insight into the history of "intelligence" (the word, the socially constructed concept, etc) helps wrap one's head around what it means when people working in CS try to repurpose its terminology in their own field.
- tptacek 2y ago
  IQ is as far as I can tell quite well accepted as a diagnostic tool. The pushback is in its application across whole populations.
  - hirvi74 2y ago
    FWIW, anecdotal data is also considered a valid diagnostic tool too, and we know how unreliable such information can be. Also, by populations, do you mean groups of particular types of people or just groups of people in general? If anything, I thought IQ really only had anything close to merit at large population levels. Much of what I have read clearly fails at an individual level. However, if you are talking about IQ's application in regards to populations like one race vs. another, then yes, I think the pushback is well deserved.
    - tptacek 2y ago
      I agree with you about your last statement! I think it's actually a pretty interesting comparable to BMI. BMI: useful epidemiologically, across large populations, but much less useful individually. IQ: much less useful across large populations, but useful as a diagnostic/clinical tool in individual settings.
hluska 2y ago
IQ routinely gets destroyed. As an example, I was an undergraduate in the 1990s. My statistics class skewered the use of IQ back then. According to some friends with undergraduates, they still use that as an example of statistics being used badly.
- hirvi74 2y ago
  People say that, but then people like me are administered the tests for clinical diagnostic purposes (right or wrong), and even my state still considers the scores to be a valid measurement of intelligence, and thus a factor in whether someone convicted of murder is eligible for the death penalty. I think the concept is bullshit myself, but regardless the damage is done, and still being done for what it is worth.
  - Izkata 2y ago
    My crude understanding is, we don't have a good way to calibrate above-average scores, but it is a good measure for below average (provided there aren't arbitrary barriers like the language it's in).
  - hluska 2y ago
    That’s too bad, but I replied to something that claimed there is no criticism of IQ. IQ is criticized and used. Those are not exclusive states.
    - hughesjj 2y ago
      Yup. Polygraphs are still used in the intelligence community and court too. I'm seeing the tide turn (imo), but by no means am I claiming it's no longer used (regardless of merit). I acknowledge I'm starting a personal anecdote which is subject to my own biases such as cohort affects.
- Natsu 2y ago
  IQ is an interesting one. There are indeed plenty of issues in actually measuring it and deciding what we're even measuring to begin with, but at the same time, I've heard some people try to say it doesn't even exist at all. Which seems odd, because I've yet to see anyone who doesn't believe that stupidity exists and it's the other side of the same coin.
buzzardbait 2y ago
IQ is definitely not spared. It doesn't take a Mensa member to realize that human intelligence cannot be reduced to a single number.

worik 2y ago

> BMI is trivial to measure conclusively That does not make BMI a good measure.

tptacek 2y ago
It does for some applications, and not for others. In epidemiology you're looking at the number across broad populations, where a lot of the "three dimensions" idiosyncrasies cancel out. You're likely to run into trouble taking literal BMI constants and turning them into individualized patient care instructions, though.
- nottorp 2y ago
  Or basically: there are outliers, and those tend to complain. But the average billions cancel them out statistically. I'm an outlier myself, and so is anyone who did some serious sports for a significant amount of time. There are other reasons to be an outlier too. But they're not so statistically significant.
  - xarope 2y ago
    ditto. Always a bit frustrating when the sadly overweight nurse looks at my height and weight, charts it, and mutters to themselves "borderline". My last visit, at least the doctor deigned to actually eyeball me and said "you look like you are quite active, we can ignore this".
    - nottorp 2y ago
      Oh I'm inarguably overweight, but not to the point the BMI would indicate, considering that when i was younger and in top form i was between 29 and 30.
- worik 2y ago
  You are saying it is a not dreadful statistical measure. That is doubtful, but possible It is used for individuals. That is where it is harmful