Thursday Throughput: Not So Fat Obesity Edition

Michael Siegel

Michael Siegel is an astronomer living in Pennsylvania. He is on Twitter, blogs at his own site, and has written a novel.

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21 Responses

  1. fillyjonk
    Ignored
    says:

    the obesity thing: some have posited that some percentage of the “poor health outcomes” in heavier (if not “morbidly obese”) people is that they tend to avoid doctors and while anecdote =/= data, that seems to ring true to me – I went from 1999 to 2012 (when I was refused from giving blood twice because my blood pressure was too high) without seeing a doctor or having a regular doctor, because I went in for a flu shot to a local physician and she wanted to write me a prescription for weight loss medications. (I am heavy, but not obese, and I work out and strive to eat healthfully).

    I was fortunate more recently to find a doctor who (mostly) doesn’t make a deal about my weight. (She did mention the 10 or so pounds I gained – which I have since lost – during the pandemic). But yeah, she has regularly commented my blood numbers are better than hers, and that’s the measure of health she prefers to go by. Also the fact that I do the equivalent of a 5K jog (just in a less-high-impact way) most days of the week.

    By the most restrictive charts, I should weigh about 140; I was 140 lbs last when Reagan was in office.Report

  2. Brandon Berg
    Ignored
    says:

    Note that failure to control for smoking will tend to bias estimates of obesity-related death downwards. Because smoking both increases mortality and suppresses weight gain, it will result in higher mortality rates for people with low BMI.

    While the Flegal study was in some ways methodologically superior to contemporary studies, it was still deeply flawed in some very important ways. Baseline morbidity is a huge problem, because there are diseases that, like smoking, tend to a) kill you, and b) cause weight loss, sometimes before diagnosis. This can be an important confounder, especially in age brackets where death is relatively rare; even a small number of people in the normal or underweight category due to cachexia can skew the mortality numbers pretty substantially.

    This is a hard problem, but a technique recently developed to sidestep it is to look at the association between lifetime maximum BMI and mortality, rather than BMI at the beginning of the study. With this technique, studies find a relationship between overweight and mortality that’s more in line with pre-Flegal expectations. Note that this does not mean that losing weight is bad for you and pointless, only that losing weight with diet and exercise is hard, and losing weight with an undiagnosed terminal disease is easy (but not recommended!)

    BMI is also problematic, because there are two types of weight with contrary effects: Adiposity increases mortality, and lean body mass decreases mortality (or at least predicts lower mortality). Especially for men, body fat percentage can differ by up to 20 percentage points for two people with the same BMI; conversely, among men with the same body fat percentage, BMI can vary by up to 10 points. Do an image search for “bmi body fat correlation” (no quotes), and take a look at the scatterplots from various studies. When we really want to know the relationship between adiposity and mortality, using BMI instead of a true measure of adiposity results in attenuation bias.

    While Flegal’s newest paper documents some really bad behavior on the part of some of her colleagues, we should not mistake that for a vindication of her findings.

    Also, while it’s true that obesity has not “skyrocketed” in the US in the 21st century, it has continued its inexorable upward climb, with the age-adjusted adult obesity rate increasing by about 10 percentage points since 2000.Report

  3. DensityDuck
    Ignored
    says:

    “There’s a quote that P.J. O’Rourke repeats in All the Trouble in the World in the context of environmental hysteria…”

    It was amusing to me that his recent omnibus reprint has all of All The Trouble In The World except that chapter…Report

  4. DensityDuck
    Ignored
    says:

    [ThTh5] Don’t bother; “Columbus proved the religious idiots wrong because they all believed the Earth was flat” is popular myth now, just like “the religious idiots excommunicated Galileo because they believed the Earth was the center of the universe”.Report

    • Reformed Republican in reply to DensityDuck
      Ignored
      says:

      He wouldn’t have proven the Earth was round even if it was commonly believed to be flat. He ended up in North America and did not circumnavigate the globe.Report

      • Brandon Berg in reply to Reformed Republican
        Ignored
        says:

        I wonder if the consensus on the circumference of the Earth changed briefly as a result of Columbus returning successfully from his voyage to the “Indies.” Did everyone just say, “Huh, I guess he was right” for a few years until they figured out that it was actually a totally different continent?Report

        • Michael Siegel in reply to Brandon Berg
          Ignored
          says:

          My memory is that people had about the right number but thought there wasn’t a landmass. Columbus, IIRC, used some odd arguments about the world being pear-shaped as to why sailing across the other ocean would work. But the correct size of the Earth was known for about 2000 years.Report

          • Michael Cain in reply to Michael Siegel
            Ignored
            says:

            Yeah, I went and looked. Eratosthenes had the circumference correct within a couple of percent. Also a remarkably accurate estimate of Earth’s axial tilt. Also a calendar that had 365 days in the year and 366 every fourth year.Report

            • Mike Schilling in reply to Michael Cain
              Ignored
              says:

              Two things happened:

              First, Strabo, a Greek geographer, philosopher, and historian, wrote about Posidonius’s estimate, which was very close to Eratosthenes’s, but got the numbers wrong. Second, the estimate was in stadia, which were different lengths in Greece and Rome. So just like today, when you can’t trust science reporting and American vs. Imperial measures confuse things, the results got garbled. There seemed to be two different classical estimates of the size of the earth, and Columbus optimistically assumed the smaller one.

              That’s a great question about whether Columbus’s return made the incorrect number more popular. No idea.

              https://en.wikipedia.org/wiki/Earth%27s_circumference#PosidoniusReport

          • Brandon Berg in reply to Michael Siegel
            Ignored
            says:

            That’s my understanding as well, but I’m curious about what happened after Columbus returned. Back in 1492, everyone’s saying, “You’ll never make it to the Indies, you idiot. The Earth’s just too damn fat. Like your head.” Then Columbus sails off muttering about how he’s going to show those jerks but good. Then he comes back months later with a tan, saying “Hey, guys. I sent you a postcard from the Indies, but I had to bring it myself because there’s no mail service yet.” When he hands them the postcard and it says, “Suck it, putas! I was right!” do most of them just accept that Columbus was in fact right about the circumference of the Earth? Or did they immediately figure out that there must be another continent in the way?Report

  5. Brandon Berg
    Ignored
    says:

    Because it seems to me that the more tenable the goal is with Americans’ weight, the more likely they are to make the choices necessary to get there. If you tell me that a weight of 205 will get me to decent health, that’s a reasonable goal I think I can reach. If you tell me that 175 is the goal — a weight I have not seen since I was in college and two inches shorter than I am today — I’m more likely to just say, “screw it, I’m doomed” and reach for some more fries.

    You may be right that many people think this way, but I think it’s the wrong way to look at. Whether the optimal weight for you is 205 or 175, 205 is still better than 235 (again, composition matters, but for simplicity I’ll ignore that here). If you can lose 30 pounds, that’s a win, even if 60 would be better. And it’s not like there’s some magic weight that makes you immortal. The absolute reduction in mortality risk from going from 235 to 205 is probably about the same either way.

    Scott Adams has kind of gone off the rails since Trump’s election, but I like his idea about systems vs. goals. What matters is not achieving some arbitrary goal, but having a system that moves you in the direction you want to go and sticking with it.Report

  6. Oscar Gordon
    Ignored
    says:

    ThTh8 – Things that cause a brain to experience a BSD.Report

  7. Michael Cain
    Ignored
    says:

    Serious hope-things-work-out wishes extended to Our Todd and Brother Burt. The weather forecast I have calls for 112 in Portland, OR on Sunday. While 72 and rain in Fort Collins, CO. Bizarre sh*t going on.Report

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