Reader Question – What is the Body Roundness Index?

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Reader Shauna asked “I just saw an article about the Body Roundness Index, is that as silly as I think it is?”

The Body Roundness Index seems to be the weight loss industry’s response to finally having to (at least begin to) admit that the Body Mass Index (BMI) is nonsense. The BMI is a ratio of weight and height that has been used to pathologize bodies based on their size alone and has its basis in racism. I talked about that in depth in this piece.

Earlier this year the AMA, which takes hundreds of thousands of dollars in donations from the weight loss industry,  tried a little sleight of hand with this, admitting that there are serious issues with the BMI (which has been used as a justification for the much of the weight loss paradigm) but instead of acknowledging that simply pathologizing bodies based on shared size is an idea lacking scientific basis and merit that has done incredible harm, they instead said that we just needed more and different ways to pathologize bodies based on shared size.

That brings us to the study Shauna sent me: “Body Roundness Index and All-Cause Mortality Among US Adults” published in JAMA (the Journal of the American Medical Association.)

The authors reported no conflicts of interest, even though one of the authors, Qiushi Lin, MD, PhD, literally works for Sanofi Aventis which just had its weight loss drug preliminarily rejected by an FDA panel.

Where the BMI is used to pathologize bodies based on weight and height, the The Body Roundness Index (BRI) uses height and waist circumference.

The specific calculation they used is “364.2 − 365.5 × √(1 − [waist circumference in centimeters / 2π]2 / [0.5 × height in meters]2)”

The use of mathematical formulas tends to lend these concepts an heir of scientific validity that they do not deserve. They explain that “Due to the lack of a reference range, BRI was categorized into 5 groups according to the 20th, 40th, 60th, and 80th quantiles to explore the association with all-cause mortality.”

They find a “U-shaped association between BRI and all-cause mortality. Our findings provide compelling evidence for the application of BRI as a noninvasive and easy to obtain screening tool for estimation of mortality risk and identification of high-risk individuals, a novel concept that could be incorporated into public health practice pending consistent validation in other independent studies.”

By this they mean that those at the lower and higher ends of this scale have higher all-cause mortality. As I’ve talked about before, one of the cornerstones of research methods is that correlation does not imply causation. The U-shaped association they found might be a valid correlation. The mistake happens if the assumption is that the BRI is the REASON for the increased risk and, when it comes to weight and health (particularly those of higher-weight people) that’s what typically happens.

That’s what I think the problem is going to be. In our culture, there is a tendency to jump at any perceived “proof,” no matter how shoddy, that being higher weight causes health issues/is a health issue. What these researchers have found is an unexplained correlation between being at lower and higher weights and higher rates of all-cause mortality. What they absolutely have not found is that being at lower and higher weight CAUSES higher rates of all cause mortality.

They don’t ever claim that they’ve found causation but then they conclude “a novel concept that could be incorporated into public health practice pending consistent validation in other independent studies” and not, for example, that causal mechanism(s) should be identified prior to foisting this formula on the public, it gives me the sense that they are jumping the gun here.

I’m not going to do a deep dive into the methodology here because the concept is so deeply flawed at its base.

I’ll start with those at lower BRI range. Their BRI could be due to extreme illness (including everything from cancer, to substance use disorders, to eating disorders and more )that are the actual reason for increased all cause mortality. What they may have found is that those in the lower BRI categories are more likely to be very ill which means their findings would not extrapolate to those at the lower end of the weight spectrum who are not experiencing illness.

When it comes to higher-weight people, we know that experiences of weight stigma, weight cycling, and healthcare inequalities are all associated with increased all-cause mortality. People with a higher BRI are more likely to have these experiences.

Not only did these study authors fail to control for these, they failed to even mention them.

Without controlling for these possible confounding variables, what their findings may indicate is just that they’ve found even more evidence that experiences of weight stigma, weight cycling, and healthcare inequalities increase all-cause mortality.

So, if the lower someone’s BRI category is, the more likely it is that they are very ill and the higher someone’s BRI category is, the more likely that they’ve experienced/experience greater weight stigma, weight cycling, and healthcare inequalities, then we would see the exact “U-shaped association between BRI and all-cause mortality” that the study authors found.

I’m not saying those are definitely the reasons, I’m saying that’s the research we should be doing, not more research to reinforce a questionable correlation until the weight loss industry starts claiming that if there are *that many* studies that show correlation then it *must be* causation.

Besides the weight loss industry (mis-)using this concept, I am worried about what this will lead to in terms of healthcare.

The weigh-ins that patients are expected/pushed to endure in order to calculate BMI already cause some patients to delay or avoid healthcare appointments. How much worse is that going to become when healthcare providers are running after patients with tape measures to get a waist circumference measurement so they can calculate BRI.

If BRI is “incorporated into public health practice” as these authors suggest using simply the correlation they’ve found, then the mostly likely outcome is that the suggestion is to manipulate BRI to improve all-cause mortality risk. This will be another way for the weight loss industry (including Sanofi Aventis if they can get their new drug into the endzone) to continue making money hand over fist, but for patients it will be the same old thing, which makes its use instead of BMI basically a distinction without a difference.

Whether it’s due to profit incentive, paradigm entrenchment, or a combination of both, the people doing this research seem to be willing to do absolutely anything other than control for confounding variables or consider the evidence that focusing on supporting health directly (rather than maintaining our obsession with weight loss,) may provide more benefits with fewer risks.

Driven by the weight loss industry, weight science has gone a long way down the wrong road and they would rather step on the gas then slow down, let alone turn around. A healthcare system that is committed to viewing the existence of higher-weight people as a problem to be solved will never create polices or interventions that truly support the physical or mental health of higher-weight people.

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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.