Study Questions Supposed Link Between Being Higher-Weight and Cognitive Ability

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Thanks to everyone who sent me this article from Medical News Today and asked me to write about it! I’ll discuss the study, but I’m also going talk about the article because it’s a great demonstration of how even articles that appear to question weight stigma can still be deeply rooted in weight stigma.

The article is called “BMI, ob*sity and cognitive ability: Study questions previously established link”

Before I get into it, I want to start by saying that the concept of “cognitive ability” is problematic and has been, and continues to be, used as a tool to forward racism, ableism, weight stigma, transphobia, homophobia and more.

The article starts:

In 2016, more than 1.9 billion adults worldwide were overweight, of which more than 650 million adults were affected by ob*sity

The “affected by ob*sity” line is right out of the weight loss industry playbook  - they are claiming that these “person-first” constructs constitute “anti-stigma” language but, in fact, it’s a massive part of their goal of having simply existing in a fat body be seen as a health condition. I wrote about this in detail here

[ob*sity] — a condition where a person’s weight is not within healthy limits, potentially causing other health concerns.

This is a weird way to say this. For starters, there is no such thing as a “healthy weight limit” (or a “healthy weight” for that matter) There can be two people of the exact same weight with vastly different health statuses, and two people with vastly different weights can have the exact same health status.  To be clear, “ob*sity” is just a ratio of weight and height. At least they used “potentially.”

Current projections state by 2025 that number will grow to 167 million adults and children will become overweight or ob*se.

First of all, projecting the number of fat people who might exist as if it’s a bad thing is, in fact, weight stigma. Beyond that, let’s remember that the most common outcome of weight loss attempts is total weight regain with up to 66% of people regaining more weight than they lost. If people are so worried about more fat people existing (and note that I don’t endorse that,) then they should tell people to stop trying intentional weight loss immediately.

Previous research shows ob*sity as a potential risk factor for a number of diseases, including diabetes, cardiovascular disease, osteoporosis, rheumatoid arthritis, and cancer.

I, again, appreciate them using “potential” to modify “risk factor” but, again, it’s still coming from a place of being fully invested in the body-size-as-disease model. In fact, the experiences of weight stigma, weight cycling, and healthcare inequality (or other potential confounding variables) may be the actual risk factor(s).

Additionally, past studies have linked ob*sity to a greater risk for cognitive decline. Now researchers from University College London cast doubt on a causal link between ob*sity and cognitive ability. They believe the existing findings linking cognitive ability and BMI are biased by shared family factors. The study was recently published in the journal PLOS Medicine.

We’ll get to this momentarily.

How do you define ob*sity? A person has ob*sity if their current weight is too high for their height. The most common way of defining whether a person has ob*sity or not is through the body mass index (BMI).

I have to point out that, based on this definition, you could say that a person is “ob*se” if their height is too low for their weight. This makes it sound like there is some factual basis upon which this is built. In reality, it’s based on BMI which, in turn, is based on the sketchy work of an 1800’s statistician and a whole bunch of modern profit motives.

Moving on, let’s talk about this study.

Just for starters, I think the quotes that the authors offer in the article as well as the “why was the study done” make it clear that they are still fully committed to a body-size-as-disease model and they are invested in the idea of trying to discover why people are fat so that they can determine a path to prevent/eradicate fatness. So while, as we’ll see, their study questions assumptions about size and cognitive health, they are still viewing their results through a lens of weight stigma and fat eradication.

For background, previous studies (of people who are not related) have suggested that adolescents with higher cognitive ability become thinner adults, specifically that, adjusting for family socioeconomic position, moving from the 25th to 75th percentile of adolescent cognitive ability was associated with an estimated -0.61 kg/m2 decrease in adult BMI.

The first thing I want to point out is that this is still a difference of less than 1 BMI point. Note that there is no causal mechanism established and there are lots of possible confounding variables here (including experiences of weight stigma, weight cycling, and healthcare inequalities) that this new study doesn’t take into account. The goal of this new study is to attempt to control for shared family factors (including genetics, socioeconomic status, parenting style including food choices, and parental cognitive ability). While this study doesn’t look at individual shared family factors, it tries to control for them generally by studying siblings.

This study found that moving from the 25th to 75th percentile of adolescent cognitive ability was associated with just a −0.06 kg/m² decrease in adult BMI.

Going back to the article, this is when it takes a sharp turn into stereotype town. In explaining the results, the study’s lead author says:

Two possibilities for this small association are that one, our results were biased towards finding smaller associations (e.g. by siblings influencing each other) and two, reflective decision-making isn’t so important in determining BMI as other factors like satiety, etc.,” Dr. Wright added. “Both of these are speculative.”

So, let’s look at that second possibility because that’s where we get into a serious issue. The premise here, which may be obvious but I want to write it out anyway, is that being fat is the result of bad choices. So, the question that this research (both earlier research with unrelated subjects and this new study) is trying to answer is if the reason people become fat is that they lack the cognitive ability to make choices that will keep them from becoming fat.

Even in questioning that in the quote above, the study authors are still saying that if reflective decision-making isn’t what makes people fat then we should look to things like satiety with no discussion, for example, of the idea that body diversity is simply part of the natural order of things.

The amount of money that is spent on research trying to figure out what fat people do “wrong” that makes us fat and what could be done to eradicate fat people and prevent any more from existing is staggering and, as far as I’m concerned, absolutely wasted. Let’s pour that money into things that would actually help - like studies to create best practices in surgery and pharmacotherapy for supporting the health of fat people (rather than BMI-Based denials and a laser focus on things that might make us temporarily a bit thinner.) Let’s stop trying to eradicate fat people from the world, and start creating a world where fat people can thrive.

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More research and resources:
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*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings’ Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison’s Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.