From COVID-19’s inception in China in December of 2019 to the present time, those individuals with comorbidities, such as obesity, hypertension, diabetes, cardiovascular disease, and pulmonary dysfunction were at greater risk to become severely ill.
As the virus spread around the world, it became apparent that a much higher number of people, who were overweight and obese, were being admitted to the hospital—with advancing illness, or critically ill at the time of admission.
The statistics from Italy, the United Kingdom, France, and the United States verified that there was an association with COVID-19 severity with obese patients. However, it was only partially due to obesity’s inherent comorbidity risks.
According to “COVID-19 and Obesity,” which appeared in the August 2020 issue of Practical Diabetes, “an analysis of more than 20,000 hospitalized patients in the UK identified obesity, as a major independent risk factor for COVID?19 severity and mortality.”
In addition, “two recent studies of Chinese COVID-19 patients also identified obesity, as an independent risk factor–concluding that patients with obesity are three times more likely to develop severe symptoms compared with normal0weight patients, and each unit increase in body mass index was associated with a 13% increase in the risk of severe COVID-19.”
The journal article points to the fact that research from the 2009 influenza A H1N1 pandemic demonstrated that obese individuals had twice the mortality rate of people with normal weight. And, “the mounting evidence (shows) that obesity increases the risk of respiratory diseases and respiratory tract infections, including obesity hypoventilation syndrome, asthma, pulmonary embolism, influenza, and community acquired pneumonia.”
The excess visceral adipose tissue (VAT) in the abdominal cavity, that has an immunomodulatory effect, has been determined to be an important factor in the link between obesity and respiratory infection, despite not being fully understood.
“Through the secretion of adipokines, such as adiponectin and leptin, adipose tissue modulates innate and adaptive immune responses. When VAT becomes dysfunctional in obesity, secretion of adiponectin is reduced and leptin increased–resulting in immune dysregulation,” comment the journal authors from the United Kingdom.
The UK authors also point to a link between low Vitamin D status and obesity. “The reason for the strong association between obesity and vitamin D deficiency is unclear, but the leading theory is that dysfunctional adipose tissue in obesity sequesters vitamin D and impairs its release, so it is no longer bio-available.”
Vitamin D has an essential role in immune function. “People with obesity,” note the British authors, “need to produce or consume more vitamin D than people of normal weight, in order to maintain adequate circulating levels of the vitamin.”
The investigators conclude by saying that, “there is mounting evidence that obesity is a major risk factor for severe illness and mortality from COVID-19. Research is urgently needed to elucidate the mechanisms by which obesity contributes to the severity of COVID-19 illness, in order to identify potential targets for treatment.”