Novel Coronavirus SARS-CoV-2

Obesity and Coronavirus Infection Risk? Not So Fast

For some time, it’s been clear enough that obesity increases the risk for severe symptoms with COVID-19. CDC warns that even mere overweight status might be a source of risk. But what about the risk of infection in the first place? Some studies suggest a link. However, we would advise caution in accepting that conclusion. A new study, awaiting peer review, offers prospective evidence that obesity does not confer an increased risk of coronavirus infection.

A Large, Prospective Cohort

This study is unique because it’s a prospective study of nearly 5,000 employees at SpaceX. In other words, it’s not a backwards look at people who got sick with the virus to fish around for a correlation. Eric Nilles studied a cohort of 4,469 employees who volunteered for the study. Researchers followed them from April through July this year. The employees came from four different states and seven different work sites.

In this cohort, the virus wound up infecting 322 individuals. Obesity made no difference in the risk of infection. It also made no difference in the immune response of people with the infection. Where it did make the difference was in symptoms. Individuals with obesity were more likely to have a fever and multiple other symptoms.

Calling Earlier Claims into Question

All this is consistent with the CDC warning that obesity raises the risk for more severe symptoms with the novel coronavirus infection. But it contradicts the notion that people with obesity have a greater risk of becoming infected.

Back in August, an analysis by Barry Popkin et al created quite a buzz on the internet. Based on a pooled analysis of mostly retrospective studies, they found an association between obesity and coronavirus infection risk. But the problem is that these are mostly if not all patients with symptoms. Since we know that people with obesity are more likely to have symptoms and to have more severe symptoms, this creates a systematic bias.

The buzz from this study came from a claim that people with obesity have less of an immune response to the virus. Thus, the authors expressed “a major concern that vaccines will be less effective for people with obesity.” That’s great clickbait. So it continues to generate a buzz on social media.

Again, though, that finding was based on samples of people who were already sick with the virus. So people with obesity who mounted a better response to the virus and remained asymptomatic were not represented.

Beware of Correlations

The newer study still needs peer review. But its findings remind us to beware of correlations based on retrospective data. From what we can see, it’s not reasonable to assume that people with obesity won’t respond to a COVID vaccine as well as others. True, it seems that obesity raises the risk of symptomatic coronavirus infections. It raises the risk for bad outcomes. It does not, however, raise the risk of infection across the board.

Click here for the study by Nilles et al, here and here for further perspective on it. For the Popkin study, click here.

Novel Coronavirus SARS-CoV-2, transmission electron microscope image by NIAID / flickr

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November 23, 2020

2 Responses to “Obesity and Coronavirus Infection Risk? Not So Fast”

  1. November 23, 2020 at 9:34 am, David Brown said:

    Mayo Clinic researcher Vijay P. Singh has noted that unsaturated fatty acid (UFA) toxicity “is very relevant” in an acute disease such as COVID-19 which progresses “rapidly over days or even hours, in contrast to chronic diseases like hypertension and diabetes, which progress over months to decades.”

    Singh also points out that “not all obesity is the same. It is the UFA component in obesity that determines the degree of harm in the event of acute lipolysis as in severe COVID-19… A larger proportion of UFA accumulation in adipose fat — even when the overall fat amount is lower, as in a leaner person — may be more harmful during acute lipolysis than a greater proportion of saturated fat.”

    Singh further comments, “Dietary habits, that is, the fats we cook in such as butter and different types of oil, as well as the foods we eat, are strongly determined by culture, region, tradition, and what we’re taught is good or bad, though there is little evidence for the latter.”

    Singh’s most important point: “In the long term, avoiding high UFA intake may help with future pandemics like COVID-19…”

    • November 23, 2020 at 10:49 am, Ted said:

      The data referenced in this comment are from “small and retrospective and … correlative” studies. These observations offer a basis for speculation, but do not provide definitive evidence about a role for unsaturated fatty acids in COVID-19.