Latest evidence on obesity and COVID-19
A summary of the evidence so far suggests that obesity is associated with a higher risk of developing severe symptoms and complications of coronavirus disease 19 (COVID-19), independent of other illnesses, such as cardiovascular disease.
Early data seems to suggest that people with obesity are more likely to become severely ill due to COVID-19, the disease caused by the novel coronavirus.
An increasing number of reports have linked obesity to coronavirus mortality, and the Centers for Disease Control and Prevention (CDC) now list severe obesity as a risk factor for severe COVID-19. The CDC define severe obesity as having a body mass index (BMI) of 40 or above.
However, it is currently unclear exactly why obesity is associated with a more dangerous form of the disease.
To shed light on the situation, a team of experts in Germany, the United Kingdom, and the United States have come together to review the evidence and clarify what we know so far.
Their findings are published in Nature Reviews Endocrinology.
The evidence so far
The article summarizes the preliminary data available on obesity and COVID-19.
In China, where the outbreak began, data from 383 patients showed that having obesity was associated with a 142% higher risk of developing severe pneumonia associated with COVID-19.
A larger study of over 4,000 patients with COVID-19 in New York City found that severe obesity was a major risk factor for hospitalization, second only to age.
In Seattle, a study of critically ill COVID-19 patients made similar findings. This analysis found that 85% of patients with obesity required mechanical ventilation, compared to 64% of patients without the condition. Moreover, 62% of the patients with obesity died of COVID-19, compared with 36% of those without obesity.
However, it is important to note that this particular study included only 24 patients, all of whom were critically ill, making it difficult to draw far-reaching conclusions from the data.
The final study included in the analysis involved 124 patients in Lille, France, and also found that patients with obesity were more likely to require invasive mechanical ventilation.
Together, the evidence suggests obesity may be a significant risk factor for COVID-19.
As the lead author of the study, Dr. Norbert Stefan, of the German Center for Diabetes Research, explained to Medical News Today:
"We concluded that obesity may put people infected with the novel coronavirus (SARS-CoV-2) at a very high risk for a more severe COVID-19 illness and possibly risk of death."
Why is obesity a risk factor?
Importantly, the risk appears to be independent of other illnesses, such as high blood pressure, that are more prevalent in people with obesity.
According to the study authors, one way that obesity might increase the risk of severe COVID-19 involves respiratory dysfunction.
People with obesity are more likely to have higher resistance in their airways, lower lung volumes, and weaker respiratory muscles, which are critical in the defense against COVID-19. These factors make an individual more likely to develop pneumonia, and they place additional stress on the heart.
Obesity is also associated with diabetes, heart disease, and kidney disease, all of which likewise increase the risk of developing pneumonia.
Setting these issues aside, high blood pressure, high cholesterol levels, and prediabetes could make people more susceptible to infection, the authors point out.
The connection between the makings of diabetes and COVID-19 appears to be particularly important.
"There is data emerging showing that hyperglycemia [high levels of glucose in the blood], even in the range where diabetes cannot be diagnosed, is a strong and independent predictor of a severe course of COVID-19," explains Dr. Stefan.
Missing BMI data
While this research strongly suggests that people with obesity experience more risk associated with COVID-19, there are limitations to the analysis. First, most studies to date have not been peer-reviewed.
Also, many did not provide measurements of the patients’ weight or height, both of which are necessary to calculate BMI, a universal measure of obesity. BMI can also be used to estimate the percentage of body fat.
"Most of the articles that were published during the last 2 months reporting data about comorbid conditions, which may be associated with increased risk of severe COVID-19, did not provide data about body fat mass or metabolic health," says Dr. Stefan. In particular, some studies from China and Lombardy, Italy — two of the worst-hit areas — did not provide weight or height data.
The authors emphasize that future studies should not only record BMI but also waist circumference, as well as levels of glucose and the hormone that regulates it, insulin. These measurements can help determine whether a person has insulin resistance or prediabetes, which may contribute to the higher risk of COVID-19 in people with obesity.
Eleanor Bird for MedicalNewsToday