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  • Writer's pictureP.K. Peterson

COVID-19: Does Obesity Matter?

“To say that obesity is caused by merely consuming too many calories is like saying that the only cause of the American Revolution was the Boston Tea Party.” - Adelle Davis, American author and nutritionist

“Issues like obesity do, as you well know, have a knock-on effect to diabetes. So we all are better off if we invest early in prevention.”

- Jacinda Arden, Prime Minister of New Zealand

Have you gained weight during this pandemic? I have…but there is no mystery as to why. I have been eating more junk food and exercising less. For the first time in my life I find that I’m officially overweight! (According to the criteria of the Center for Disease Control and Prevention [CDC] “overweight” is defined as an increased Body Mass Index [BMI] of 25 through 29. If you’re curious about your BMI, visit the CDC’s nifty Adult BMI Calculator on its website []). And I’ve read several publications that suggest that the risk of severe COVID-19 is even greater for people who are overweight than those who are obese (BMI starting at 30). This raised my concern: Is my being overweight another factor to add to my gender and age that puts me at an increased risk of severe COVID-19? In this Germ Gem post, I discuss the link between being overweight or obese and COVID-19.

The obesity pandemic. Obesity is a huge problem globally. Generally, it is much more prevalent in low income as opposed to high-income countries. Nonetheless, you may be surprised to learn that according to the World Health Organization, Vietnam, a low-income nation, is the least obese country in the world (only 2.1% of their population is classified as obese). Contrast that with the United States that is the most obese (36.2% of the adult population) among the 10 most obese countries in the rich OECD (Organization for Economic Co-operation and Development) countries.

The skinny on fat. Body fat or adipose tissue is a loose connective tissue composed mainly of adipocytes that store energy in the form of lipids. There is, however, much more to fat than what meets the eye. For example, fat tissue contains the largest volume of adult stem cells, a source of stem cell transplants. In recent years, fat also has been recognized as a major endocrine organ and to contain immune cells, such as, macrophages and T cells. These cells can play a role in defense against pathogens. When activated, however, they release cytokines, which as you may recall from previous Germ Gem posts, can result in a “cytokine storm” that damages vital organs.

Obesity and the risk of infections. For most of my career, obesity wasn’t considered a risk factor for severe infection. It wasn’t until the 2009 swine flu pandemic—when I was asked to consult on a 32-year-old otherwise healthy obese woman who unfortunately subsequently died—that I became aware of obesity as a potential risk factor for severe infection. Subsequent research found that obesity can play a role in the pathogenesis of a number of infections. In 2019 in the International Journal of Epidemiology, a Swedish study reported an increased incidence in obese women and men of infections of the skin, gastrointestinal tract, urinary tract, and of life-threatening sepsis.

Obesity as a risk factor for severe COVID-19. Given this background, no one was surprised when, in the early studies of the pandemic, obesity emerged as a risk factor for severe COVID-19. According to the CDC, obesity not only increases the risk of severe illness and death of COVID-19 patients, but, based on experience with vaccines against other pathogens, researchers believe that obesity may also blunt the response to vaccines against SARS-CoV-2 once they become available. The CDC also notes that obesity disproportionately impacts non-Hispanic Black adults.

In August, the American nutrition and obesity researcher Barry Popkin and his colleagues reported a comprehensive study of obesity and COVID-19 in the journal Obesity Reviews. They concluded “[I]f you contract COVID-19, you have more than double the likelihood of going into the hospital if you’re obese and 50% more likelihood of dying.” In early September, Dr. Dror Dicker, President of the Israeli Association for the Study of Obesity, reported that individuals with a BMI > 30 became COVID-19 negative 5 days later than those with a normal BMI. This finding appeared to be associated with a higher viral load in obese patients related to increased levels of ACE2 receptors in adipose tissue. (ACE2 receptors are used by SARS-CoV-2 to enter cells.)

It’s still an open question. In what appears to be a prescient article in April in the American magazine WIRED (“Covid-19 Does Not Discriminate by Body Weight”), author and dietitian nutritionist, Christy Harrison, debunked the claim that those with higher BMIs are at special risk of dying from COVID-19. Instead she makes the case that all the reports up until then were flawed by not controlling for social determinants of health, such as, race, socioeconomic status, or quality of care. Also, she pointed out that obesity is associated with a significantly lower risk of dying from some diseases, such as, acute respiratory distress syndrome (ARDS), pneumonia, diabetes-related hospitalization—the so-called “obesity paradox.” Finally, she believes “weight stigma” and “anti-fat attitudes” are the problem—…“stigma is what truly jeopardizes their health, not weight itself.”

Aligned with Harrison’s views is a report from the Veteran’s Administration (VA) that appeared on September 23 in JAMA Network Open, “Risk Factors for Hospitalization, Mechanical Ventilation, or Death Among 10031 US Veterans With SARS-CoV-2 Infection.” In this carefully controlled, large study, most COVID-19 deaths were associated with older age, male sex, and comorbidity conditions that had previously been identified in smaller studies. Remarkably, however, many factors previously reported in smaller studies to be associated with mortality were not among them, such as obesity, Black race, Hispanic ethnicity, chronic obstructive pulmonary disease, hypertension, and smoking.

Weighing the evidence. If you share my opinion that the definition of a scientific “discovery” is finding something you didn’t expect, the VA study represents a discovery. Yet as the authors of the VA study point out, their findings may not be generalizable to other populations, especially women. Nonetheless, this study deserves our serious attention.

Teasing out the role of obesity as a risk factor for severe COVID-19 isn’t easy because obesity is a component of what’s called the metabolic syndrome defined as “a cluster of conditions that occur together and increase your risk of heart disease, stroke and type 2 diabetes. These conditions include increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels.” While obesity by itself may look like a risk factor for severe COVID-19, when subjected to multifactorial analyses the risk may not hold up because of these or other confounding conditions.

Thus, my answer to the question, “COVID-19: Does obesity matter?” is: “Stay tuned.” In my opinion, additional carefully controlled studies are required before a conclusion can be reached. Irrespective of whether obesity is a COVID-19 risk factor or not, however, we all know that being overweight or obese is not healthy for anyone. For now, I’m not adding being overweight to my risk factors for severe COVID. My gender and age, and the dread of the approaching Minnesota winter are enough for me to worry about!

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Main Page images courtesy of Shuxian Hu, MD. Dr. Hu is a scientist in the Neuroimmunology Research Laboratory at the University of Minnesota.

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