Grasping at straws: Rushing to dismiss the latest ‘Overweight people live longer’ study

I think I first heard from Brian/BStu/Red No. 3 the observation that if a study seems to show benefits to being thin, it’s accepted at face value, but if a study seems to show benefits to being fat, it’s always questioned and people attempt to explain it away. (Also, people try to explain away studies that show disadvantages to being underweight or in the thinner half of ‘normal’.)

I think after this latest study, we can say with confidence that the conclusion that ‘overweight’ people live the longest is not going away. But people are rushing to explain it away. William Saletan runs down the list of explaining-away explanations that have been proposed.

Fat is bad for you, right? That’s what doctors tell us. But a review of nearly 100 studies, published this week in the Journal of the American Medical Association, confirms previous indications that the story is more complex. Being overweight or even mildly obese, as measured by body mass index, doesn’t make you more likely to die than a person of normal weight. It makes you slightly less likely to die.

How can this be? Is fat good for you?

That’s the wrong conclusion, according to epidemiologists. They insist that, in general, excess weight is dangerous. But then they have to explain why the mortality-to-weight correlation runs the wrong way. The result is a messy, collective scramble for excuses and explanations that can make the new data fit the old ideas. Here’s what they’ve come up with…

Interestingly, although it seems clear that Saletan isn’t too impressed with most of these explanations, the promotey-graphic-thingy at the top of Slate’s page where they put the featured stories made it look the opposite. I should have done a screen-capture of it, but IIRC it said “Do overweight people live longer? Why it’s not that simple”, or something to that effect. I’m pretty sure of the “not that simple” part, anyway.

Anyway, I can’t see any good reason to try to explain away the reduced death risk* for ‘overweight’ people but accept at face value an increased risk of death in BMIs >35 (the start of the ‘class II obesity’ category). If you accept that some BMI categories increase risk of death, I don’t think you can make exceptions for the ones you like better.

Some of the things on the list aren’t even examples of explaining the results away, though; they’re admissions that being ‘overweight’ does lower your risk of death.

4. The dangers of being underweight hide the dangers of being overweight. A JAMA editorial notes that people in the thinner half of the “normal” BMI range have a higher mortality rate than those in the plumper half. This thinner subset inflates the normal-weight group’s mortality rate, which makes the mortality rate among overweight and obese people look good by comparison. The solution is to shift the whole scale to the right, so that these thin people are recognized as underweight, while people presently labeled overweight are redefined as normal weight. Once we’ve completed this reallocation, it will be clear once again that overweight people—now defined to include many whose BMI would previously have put them in the obese category—are at higher risk of death than the newly reclassified normal-weight people are. The value of weight control will be reaffirmed, but the thresholds will have changed.

So, the result is still that people with a BMI between 25 and 30 are at a low risk of death compared to those with a ‘normal’ BMI.

7. Fat protects you against injury. Many old people die from falls. Chubbier people “have more padding to protect the bones should a patient take a tumble, lowering the risk of a life-endangering hip fracture,” notes the Los Angeles Times.

Once again, this does nothing to contradict the finding that people with a BMI between 25 and 30 are at a low risk of death. This only supports the idea that being in the ‘overweight’ category is good for you. I don’t see any reason to decide that diseases for which obesity is a risk factor ‘count’ but diseases for which obesity lowers the risk don’t.

*Yeah, I know, “risk of death” sounds weird given that everyone is at a 100% risk of death eventually. What it means is the risk of dying within a specific time period–whatever time period a particular study is looking at.

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10 Responses to Grasping at straws: Rushing to dismiss the latest ‘Overweight people live longer’ study

  1. Annabelle says:

    What about morbidity versus mortality?

    • The study didn’t look at morbidity, it just looked at mortality.

    • Exactly. And it’s morbidity that’s the real issue.

      ‘Real’ according to who? I keep alternating between a charitable reading of your comment, along the lines of “I’m disappointed that they didn’t look at the issue I’m interested in,” and an uncharitable one, something like “They didn’t look at the obviously objectively important issue, which is synonymous with the issue I care about.”

      I’m also not sure if you’re trying to criticize me/Paul Campos/everyone talking about it because we’re not specifically addressing morbidity, or if you think that the authors were wrong to not study the issue you wanted them to study.

      Surely you realize that if it weren’t for studies like the ones the meta-analysis is analyzing, you wouldn’t even be able to say that “the real issue” is morbidity? Unless you just think that morbidity is always more important than mortality in a general sense, not just in looking at which one is more affected by fat. If that’s the case, be aware that there are people who disagree with you. For example, I wrote on FaceBook that I wondered if weight loss surgery increased longevity at the expense of quality of life (I’ve heard conflicting reports about whether it increases or decreases death risk), and one of my FaceBook friends wrote that she would rather have longevity than quality of life. (FWIW, she is thin and disabled enough for it to affect her quality of life, so she has experience with lowered quality of life.)

      • Michelle says:

        I was just thinking the same thing – why, pray tell, is morbidity more “real” than mortality? I’ve actually heard this argument before when speaking in defense of HAES, and there was recently a (disgustingly ableist) piece in the National Post about life expectancy increasing, but also the rates of chronic illness increasing, and HOW AWFUL THAT IS WHAT A TRAGEDY LET’S ALL JUST KILL OURSELVES. I wish I were exaggerating, but the headline actually said, “You’ll live longer, but wish you were dead.” Um, speak for yourself, asshole? Morbidity is important, but it is not the “real” issue. In order for us to address morbidity, people have to, like, be ALIVE first. Yay! Another issue that is equally “real” to morbidity is how we 1) define and diagnose disease, and 2) how we treat disease, both medically and socially. Okay, so since the germ theory of disease allowed us to get rid of several pesky communicable illnesses that used to kill people before they reached advanced ages, our burden of disease is more swayed toward chronic illnesses. This is actually a step in the right direction, despite death-denialists clutching their pearls about the presence of death and disease at all. Yes, we all die at some point! I know it is scary! But guess what, it is also probably inevitable. And a large number of people experiencing illness or impairment of some kind along the road of life, or before death, is also inevitable. So maybe we should think about how to deal with that so people can live lives of quality rather than being written off as non-entities who would be better off dead. JUST A THOUGHT.

      • “Just” a thought, or AN AWESOME THOUGHT?

        One thing that makes it hard to weigh morbidity vs. mortality, as well, is that death is basically a binary (you’re either dead or you’re not, with the exception of things like comas where we can’t tell from the outside), but if you’re looking at morbidity, well, it may make a big difference in people’s quality of life whether they are a type II diabetic who only has to watch glycemic index of meals and is otherwise unaffected by the disease, or one who’s dependent on dialysis. It’s not impossible to get a rough measure of things like quality of life, but it’s a lot trickier to study.

  2. The Real Cie says:

    Different body types have different advantages and disadvantages. The hatred of larger body types is perpetuated, of course, by the multi-billion dollar diet industry, which could not survive without people hating themselves for their weight.

  3. DebraSY says:

    As I understand it, current BMI classifications came from the World Health Organization and are more useful in helping us determine which countries may need food assistance. The bottom of “normal” or “healthy” being set at 18.5 is only an indicator that people aren’t at heightened need.

    Clearly, an 18.5 BMI is spare and not, in itself, and indicator of superb health. Moreover, those who have some excess to assist them in the event they contract a major body-wasting disease, such as cancer, obviously will show benefit in their mortality rates. This study confirms common sense.

    The BMI needs to be stripped of its perjorative classifications. Those doctors who press their patients to get below a particular number, such as 25, simply because of an arbitrarily assigned adjective, are ignorant. Insurance companies who base rates on these adjectives are being fool hardy with their own profits.

    Thoughts for the day.

    • I didn’t know that about the WHO. It does seem like common sense that a BMI just above “needs food aid” would not be healthy–and yet most laypeople seem to think it’s best to be as low as possible without being underweight. (Then there’s the ones who don’t seem to think that being underweight is really a problem…)

      Always glad to see you stop by, Debra.

  4. Pingback: Abigail Saguy on Health Care Provider Bias | closetpuritan

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