Reader Question - What Does It Mean For Weight To Be A Risk Factor?

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I received this question from reader Jeff

“I read several articles recently that say that being “overw*ight” or “ob*se” is a “risk factor” for getting a health issue. Can you tell me what that means exactly?”

Technically, a risk factor for a health issue is something that increases the risk of developing that health issue (for example, smoking is a risk factor for lung cancer.) Often articles and even studies will say that being higher-weight is a “risk factor” for a health issue in a way that strongly implies that being higher-weight causes the increased risk, even though no causal mechanism is known. Often, especially in colloquial use, saying that being higher-weight is a “risk factor” for a health issue is another way to say that being higher-weight is correlated with a health issue, which is to say that they happen at the same time with some frequency, but there is no established causality.

The distinction between correlation and causation is critically important. If we find that two things happen at the same time (are correlated) we can’t assume that one causes the other. This is an important difference, and one that the diet industry and others interested in pathologizing higher-weight bodies (for profit) often try to obfuscate, because if we scratch beneath the surface we learn that other “risk factors” for those same health issues typically include weight stigma, weight cycling, and/or healthcare inequalities. For example in their 2011 paper, Bacon and Aphramor point out that the entirety of excess mortality that was attributed to “ob*sity”* in both Framingham and the NHANES could in fact be due to the harm of weight cycling (or yo-yo dieting).

In truth, in western culture it’s almost impossible to study the supposed health impacts of being fat without also studying the impacts of weight stigma, weight cycling, and healthcare inequalities, since almost all fat people are exposed to them. As someone who spends a fairly large…some might say ridiculous…amount of time reading these kinds of studies, I can tell you that they almost never even discuss these things, let alone control for them as the confounding variables they are. These correlation vs causation errors (one of the most basic concepts in research methods) are harming and killing fat patients.

Fat people aren’t the only group who are harmed by this phenomenon. In another example, many studies and articles claim that “race” is a risk factor for various health issues, when the true risk factor is having experienced racism. This can mean that fat people of color are at double risk for the harm done by these correlation/causation mistakes (which adds to the fact that weight stigma is rooted in, and inextricable from, racism and anti-Blackness*).

Whenever this kind of verbiage is used (being higher-weight is a “risk factor for” or “linked to “ etc. a health condition) it should trigger us to start asking questions - has a causal mechanism been established, or is this just correlation? Did they study/control for weight stigma, weight cycling, and healthcare inequalities? Are the people pushing this narrative profiting from creating a misunderstanding that “risk factor for” means “caused by”? Fatphobia in our culture has created a situation where people who should absolutely know better see correlation between being higher weight and a health issue and jump to causation without a second thought.

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More research and resources:
https://haeshealthsheets.com/resources/

*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.