Why obesity increases risk of Covid-19 severity?

obese man


Early on in the SARS-CoV-2 pandemic, a glaring observation was made: Individuals who were obese had a greater risk of not only developing Covid-19 infection, but also a greater risk for hospitalization for severe illness and higher mortality from it. Other trends identified as risk factors for severe Covid-19 were obesity-related comorbidities such as heart disease, type 2 diabetes, asthma, and those ages 65 and older.

National statistics have shown obesity, defined as having a body mass index (BMI) of 30 or higher, increases a person’s risk for severe Covid-19 disease than someone with a lower BMI. If a person’s BMI is over 40, their risk doubles and for people under 55, obesity is the no. 1 risk factor for developing a severe case of Covid-19.

Of course, the most troubling finding of the relationship between obesity and Covid-19 is the fact that obese individuals are more likely to succumb to this infection than others. Studies so far have shown Covid-19 patients who are obese, have a three-fold increased risk of death in those with a BMI >25, a seven-fold increased need for respiratory support in those with a BMI >25, and double the risk of severe illness in those with a BMI >30.

Part of what has driven the high global incidence of Covid-19 infection rates has been the high prevalence of obesity around the world. But what is it about carrying excess weight and adipose tissue that increases a person’s risk for developing a more concerning and severe case of this virus than someone who weighs less?

Factors of obesity affecting normal body function

To understand the relationship between obesity and Covid-19 is not straightforward. It’s complex and has many multilayer factors contributing to this phenomenon. One factor is that when a person carries excess weight, they tend to have other chronic health conditions such as high blood pressure and diabetes, making it harder to fight off the infection once it takes hold.

When someone is obese, this means they have larger amounts of fat or adipose tissue distributed throughout their body. These larger amounts of fat can compress the lower parts of the lungs making it difficult for an obese person to breathe. Blood clot development has been a major concern of patients with the illness that has certainly affected those with obesity.  The blood of an obese person is likely more prone to clotting which can plug tiny vessels throughout the body leading to the inability of oxygen to reach body tissues.

Adipose tissue is an active tissue that is able to make and send out hormones signaling nearby cells to perform inadequately. The more adipose tissue a person has, this may be resulting in a delayed response to this illness. That’s because fat appears to reduce the body’s initial immune response to the virus, allowing it to spread unchecked before it is discovered and too late to treat properly.

But probably the factor that appears to significantly make it more difficult for an obese person to fight off Covid-19 successfully is the greater expression of angiotensin-converting enzyme (ACE2) protein in adipose tissue. In order for SARS-CoV-2 to enter into a cell, ACE2 is the protein receptor allowing this virus to accomplish this feat. Fat tissue has higher levels of ACE2 than the lungs do, which is a major organ affected by Covid-19. Since individuals with obesity have more adipose tissue along with an increased number of ACE2 expressing cells, this can result in prolonged viral shedding and may ultimately lead to the dangerous and deadly cytokine storm.

Cytokine storm has been described as an immune system gone wild. The body produces cytokines, a hormone of the immune system, to help fight off bacteria, viruses, and other invading organisms. These proteins can have pro-inflammatory abilities to attract white blood cells to the site of infection to destroy the antigen.  However, there are also anti-inflammatory cytokines that do just the opposite of tempering an immune response when needed.

A cytokine storm is when the pro-inflammatory cytokines get out of control. The immune system in this scenario has become overly activated which leads to lots of energy from the pro-inflammatory cytokines that can shut down multi-organ systems possibly leading to death. Cytokine storms can lead to significant lung damage, bleeding, and clotting issues, making these patients much sicker than others with this same illness. In the case of Covid-19, patients likely will have respiratory distress due to trouble with oxygenation.

Ways obese individuals can stay Covid-free

Carrying excess weight automatically places a person in a high-risk category for a severe case if they become ill with Covid-19. Prevention of contracting the virus will be of utmost importance to protect themselves and others.  Here are best practices all of us can do daily to avoid serious Covid-19 complications:

  • Wear a mask when in public
  • Avoid large gatherings, non-essential travel, and people who are sick
  • Avoid touching your eyes, nose, and mouth
  • Practice physical distancing
  • Wash hands preferably with warm, soapy water frequently throughout the day
  • If you feel sick (fever, cough, congestion, sore throat, fatigue, loss of smell or taste, shortness of breath) contact your healthcare provider and/or be tested for Covid-19
  • If overweight to obese, begin a weight loss program by choosing healthy foods, regular exercise, and obtaining adequate sleep
Why obesity increases risk of Covid-19 severity?
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Dr. David Samadi

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Dr. David Samadi