Why is being overweight or obese linked to COVID-19?

In this video, Simon Cork, Teaching Fellow in Medical Education at King’s College London tell us about obesity and COVID-19.

Transcript:
Early research suggests that being overweight or obese is associated with worse outcomes following infection with COVID-19. But why might that be? We spoke to Simon Cork, Teaching Fellow in Medical Education at King’s College London to tell us more. But firstly, how is obesity defined?

Obesity is defined generally as someone who has a body mass index or a BMI which is greater than 30. If someone has a BMI over 25, they are considered to be overweight.

Body mass index, or BMI, is calculated as someone's weight in kilograms divided by their height in metres squared. It’s not a perfect measure, for example it cannot determine the difference between fat or muscle, but for the vast majority of the population it is a good indication of your overall fat mass. So, to what extent do we see worse outcomes for those who are overweight or obese?

What we know is that obesity is associated with a 5-fold mortality rate than people who are not obese. There was a study from Wuhan that showed that 88.2% of people in this particular study who died with COVID-19 had a BMI that was greater than 25. And in a French study, the risk of mechanical ventilation was 7 times higher in obese individuals. So we know that obesity itself seems to be associated with worse outcomes.

So, being obese is associated with more severe outcomes, but why is being obese a risk factor?

Why this is is still being researched but we know that there are likely to be multiple reasons…Obesity is associated with lower-level inflammation and one of the consequences of COVID-19 infection is that you get really high levels of inflammation as you do when you are fighting off an infection, so having a low level of inflammation seems to mean that you’re at a deficit, you have a much greater level of inflammation when it comes to being infected with the coronavirus.

When our metabolic homeostasis is disrupted, for example in obesity, low level chronic inflammation occurs. Because COVID-19 is associated with high levels of inflammation, this ‘double whammy’ of inflammation can be really dangerous. In some cases, this can lead to what’s called a 'cytokine storm' - a potentially life-threatening over-reaction of the body's immune system. And this low-level inflammation is dangerous too. It can increase the circulating levels of clotting factors, which is made worse during infection, and can lead to deadly blood clots.

So, are there other factors that might put obese individual at risk for COVID-19 complications?

Another reason is that people with obesity have reduced cardiorespiratory fitness, so they have a heightened demand for ventilation anyway at baseline they have an elevated work of breathing and diminished respiratory compliance, and all that’s at baseline. So when you add on top of that a respiratory illness, then your body doesn’t have much capacity to increase its workload, to increase its ventilation.

So being overweight or obese is associated with extra demand for oxygen, which, during an respiratory infection like COVID-19, can be serious if not enough oxygen is getting around the body. This is one reason why obesity is a risk factor for ventilation.

Finally, another reason why obesity may increase the risk of covid-19 has to do with an enzyme called ACE2. The ACE2 receptor is the main way that the virus enters the body, higher levels of this molecule are thought to be found in fatty tissue. In addition, people with diabetes are often prescribed medicines that increases the expression of this ACE2 receptor in the lungs, and so this

Видео Why is being overweight or obese linked to COVID-19? канала The Physiological Society