Study Shows Lack of Link Between High BMI and COVID Deaths

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In the early days of the pandemic studies were rushed out and highlighted in the media claiming that higher-weight people were at higher risk of COVID death. I wrote about the issues with this in my previous blog, as did Christy Harrison, Paul Campos and others.

Now an umbrella review has been published. This is a review of existing systematic reviews and metanalyses.

Quick background. A systematic review (SR) starts with a research question, creates inclusion criteria for evidence, and then attempts to gather and summarize all of the available empirical evidence that fits the inclusion criteria. A meta-analysis (MA)  is the application of statistical methods to the results of the studies collected by the systematic review. An umbrella review (UR) synthesizes all of the available systematic reviews and meta-analyses about a broad research question, typically taking into account not just the findings of the SRs and MAs, but also the quality of evidence within them. This is important because if the SR/MAs include poor quality studies, then they risk poor quality summary/analysis/conclusions.

So, this study “Risk of bias and certainty of evidence on the association between ob*sity and mortality in patients with SARS-COV-2: An umbrella review of meta-analyses” by Silva et al, 2023 looked at systemic reviews with meta-analyses (SR-MAs) “to evaluate the risk of bias and the certainty of the evidence of SR-MAs on the association between ob*sity and mortality in patients with SARS-CoV-2.”

They begin that:

“Poorly conducted SR-MAs can lead to inaccurate illustrations of evidence and misleading conclusions, leading to limited applicability.”

Then point out that:

“There are concerns that in the panic to provide answers to help administer the COVID-19 pandemic, SR-MAs are being conducted without many of the keystones of robust methods”

They sought to answer two questions with their UR:

1. What is the quality and certainty of evidence on the association between ob*sity and mortality in patients with SARS-CoV-2?

2. What is the magnitude of the association between ob*sity and mortality in patients with SARS-CoV-2 demonstrated by SR-MAs

They reviewed 24 SR-MAs from multiple countries. Ultimately they found that, while most SR-MAs did show an association between being higher weight and COVID mortality, there were serious questions as to the quality of the research that led to those conclusions.

They found that “most SR-MAs had critically low quality, and…the certainty of the evidence was very low.” In fact, in terms of certainty of evidence, 21 of the 24 SR-MAs were classified as “very low.” In terms of quality, 66.7% of the SR-MAs were “critically low quality,” and 29.2% were “low” quality. Only one of the included SR-MAs reached the “moderate” quality level and it DID NOT find a significant link between being higher-weight and COVID mortality.

The UR author’s explanation for this is that the pandemic created the need for fast information (which is, of course accurate) but that in the rush to get data “many of the keystones of robust methods are being forgotten.” I would add that, as we often talk about in research reviews here, when it comes to weight science, the keystones of robust methods are often thrown out the window regardless of how much time the authors have to conduct their research (Lucy Aphramor has an excellent piece about this.)

For example, this has happened before. During the 2009 H1N1 outbreak, fat people had poorer health outcomes (and researchers and media were quick to jump on the bandwagon of assuming that fat bodies were the cause the and trying to figure out what about fat bodies caused this.) It turns out the actual issue was that fat people were systematically treated later with antiviral medication than thin people. Per a study on the subject (Sun et. al. 2016) “After adjustment for early antiviral treatment, relationship between ob*sity and poor outcomes disappeared.”

The findings of this UR are, of course, a far cry from all the headlines claiming that being higher-weight created higher risk and from the subsequent programs and suggestions that fat people have an obligation to become thin (despite no evidence that that is even possible) as part of COVID mortality prevention. Unfortunately, when it comes to research, the media, and public health policy anti-fatness is often published, often enacted, and rarely questioned.

Frustratingly, even the UR authors in their introduction section uncritically buy in to the pathologization of body size, and the blaming of health issues/deaths on higher-weight bodies rather than, at the very least, acknowledging the confounding variables of weight stigma, weight cycling, and healthcare inequalities. Still, perhaps there is some clarity in the fact that these findings come from researchers who seem to be fully invested in the anti-fat paradigm.

Finally, I want to point out that healthcare inequalities, including everything from practitioner bias to lack of accommodating equipment (blood pressure cuffs, hospital beds, etc.) as well as medications, dosing, and clinical best practices that are created for thin bodies that may not work as well/at all for fat bodies (for example, around respirator use) can create worse outcomes for higher-weight people (which typically are subsequently blamed on their body size.) This does the most harm to those at the highest weights and those with multiple marginalized identities.

Further, I was part of a broad-based coalition that re-wrote California’s Care Rationing Protocols (the guidelines for what to do when there aren’t enough resources to treat all patients) to remove weight stigma, ableism, and racism. Still the guidelines are not law, even in California, and it is permissible in many cases for those making rationing decisions to use BMI as a reason to deny care in rationing situations. For these reasons and more, I think that the continued treatment of higher-weight people as higher-risk/higher-priority for vaccines and other treatment remains appropriate.

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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 Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.