What Researchers Know About the Obesity-COVID-19 Connection
[updated 5/5/2020] Current and past pandemics show that obesity is an independent risk factor
Updated on 4/5/2020
On 13th April, Radwan Kassir, MD, Ph.D., a bariatric surgeon at the university hospital center of Saint-Étienne, published a paper in Obesity Reviews — a high impact-factor academic journal — titled “Risk of COVID-19 for Patients With Obesity.”
There has been limited data about the link between BMI and COVID-19, Dr. Kassir admitted in an opening statement. Despite this, “the role of obesity in the COVID-19 epidemic must not be ignored,” he emphasized.
On 16th April, another peer-reviewed paper titled “Considerations for obesity, vitamin D, and physical activity amidst the COVID‐19 pandemic” was also published. Stephen Carter, Ph.D. and colleagues at Indiana University started by saying that “the link between diminished immune function and individuals with obesity raises important questions about the possibility for greater viral pathogenicity in this population.”
The Centers for Disease Control and Prevention (CDC) also acknowledge that “severe obesity, defined as a body mass index (BMI) of 40 or above, puts people at higher risk for complications from COVID-19.”
“The role of obesity in the COVID-19 epidemic must not be ignored.”
Five Theoretical Connections
 In other respiratory infections such as influenza, obesity prolongs the duration of virus shedding by 42% — making the authors conclude that obesity might promote influenza spread. “In H1N1 influenza, obesity is an independent risk factor for hospitalization and death,” Dr. Kassir added.
 ACE-2 receptors — which the COVID-19 virus binds to — is higher in adipose/fat tissues than in the lungs. “Individuals with obesity have more adipose tissue and therefore an increased number of ACE2-expressing cells and consequently a larger amount of ACE2,” Dr. Kassir cautioned.
 Adipose/fat tissue is known to serve as a reservoir for other infectious agents, such as adenovirus, cytomegalovirus, influenza A virus, HIV, T. gondii, and M. tuberculosis. [The author has previously written about adenovirus in this regard]. “By analogy, COVID-19 might also infect adipose tissue and then spread to other organs,” Dr. Kassir stated.
 Carter et al. mentioned that “increased adiposity may undermine the pulmonary microenvironment (e.g., alveoli) wherein viral pathogenesis and immune cell trafficking could contribute to a maladaptive cycle of local inflammation and secondary injury.” This simply means that obesity is linked to poor lung function and immune response.
 CDC says obesity increases the risk of respiratory distress syndrome (ARDS), a breathing difficulty common in COVID-19. ARDS also complicates the administration of respiratory support. The CDC further asserts that people with severe obesity are also more likely to have other chronic diseases that, in turn, increase the risk of severe COVID-19.
What Caloric Overload Does to the Immune System
“The Western diet appears to be mistakenly recognized by the immune system as a threat to the organism,” the professor…
What Early Clinical Studies Show
 In a Chinese study consisting of 30 medical staff, those with severe COVID-19 had a higher BMI than milder cases (27.0 ± 2.5 vs. 22.0 ± 1.3).
 In a larger study with 112 COVID-19 patients, the BMI of the severe group was also larger than the general group (25.5 vs. 22.0). The Chinese researchers further classified the patients into either survivors or non-survivors. “Among the non-survivors, 88.2% of patients had a BMI >25, which is a significantly higher proportion than in survivors (18.9%),” Dr. Kassir said.
It appears that, in this study, thrombosis — i.e., blood clot in blood vessels — was one of the major causes of death. And the risk of thrombosis is known to be higher in obese persons than non-obese. “It logically follows that obesity can be an aggravating risk factor for death from COVID-19 infection,” Dr. Kassir argued. And based on these two clinical studies Dr. Kassir reviewed, he concludes,
“Thus, we recommend extra attention and precautions for patients with obesity during this epidemic.”
Further Input from Other Clinical Studies
 In a preliminary US study (not peer-reviewed yet) involving 4,103 patients with COVID-19, Christopher Petrilli, MD, and colleagues find that “the most important features [for hospitalization] were age >65 and obesity.” They defined obesity as having BMI > 30.
In this study, obesity was also more important for hospitalization than hypertension, diabetes, coronary heart disease, cancer, kidney disease, or pulmonary disease, Dr. Leora Horwitz — senior author of the study and director of the Center for Healthcare Innovation and Delivery Science at NYU Langone — tells the New York Times.
 Another NYU Langone study, comprising 3,615 patients with COVID-19, by a different research group was recently published in Clinical Infectious Disease. “Patients aged <60 years with a BMI between 30–34 were 2 and 1.8 times more likely to be admitted to acute and critical care, respectively, compared to individuals with a BMI <30,” the physicians wrote. These odds rise to 2.2 and 3.6 times in those aged <60 years with BMI >35.
 In a France study involving 124 COVID-19 patients admitted to intensive care, half of them had obesity. Physicians find this unexpectedly high when compared to the usual rate of 25.8% for non-COVID-19 disease admitted to intensive care. The severity of COVID-19 also correlated with increasing BMI. “The need for invasive mechanical ventilation was associated with severe obesity and was independent of age, sex, diabetes, and hypertension,” the France physicians also reported, and they conclude,
“[COVID-19] patients with severe obesity should be monitored more closely.”
Summary of Contents:
Five Theoretical Connections Between Obesity and COVID-19
1. Increased virus shedding in obesity.
2. ACE-2 receptors in adipocytes.
3. Adipocytes serving as reservoir for pathogens.
4. Obesity compromises lung function and immune response.
5. Obesity increases the risk of respiratory distress syndrome and other chronic diseases.What Early Clinical Studies Show
Study #1: Higher BMI in more severe COVID-19 cases.
Study #2: Highest BMI more often seen in critical cases and non-survivors [related to thrombosis].Further Input From Other Clinical Studies
Study #3: The most important features for hospitalization were age >65 and obesity - more important than high blood pressure, diabetes, coronary disease, cancer, kidney disease, or pulmonary disease.
Study #4: Higher BMI in more severe COVID-19 cases involving younger patients.
Study #5: Obesity in more severe COVID-19 cases in need of invasive mechanical ventilation - independent of age, sex, diabetes, and hypertension.
Other academicians soon follow suit on this matter. Dr. Philip B. Maffetone, independent researcher and internationally-acclaimed author, and Paul B. Laursen, adjunct professor at Auckland University of Technology, recently published a review titled, “The Perfect Storm: Coronavirus (Covid-19) Pandemic Meets Overfat Pandemic” in the Frontiers of Public Health.
“Data from past pandemics and seasonal influenza demonstrate that obesity is an independent risk factor for severe outcomes.”
The core essence of the paper is that being obese impairs the immune system's ability to fight infections, especially respiratory ones like the flu and COVID-19. “The metabolic dysregulation of an overfat body can compromise the immune system to increase the risk of infections, and chronic respiratory diseases,” they wrote.
Past pandemics suggest a similar trend. “During and after the 2009 influenza A/H1N1 pandemic, BMI was recognized as an independent risk factor for influenza, in particular, the severity of the illness, hospitalization, increased risk of spreading the disease, and death,” Dr. Maffetone and Prof. Laursen wrote. “Data from past pandemics and seasonal influenza demonstrate that obesity is an independent risk factor for severe outcomes.”