Researchers are sounding the alarm about the link between severe illness from COVID-19 and obesity — including the impact on potential treatments.
Early in the pandemic, obesity was flagged as a significant risk factor for hospitalization, especially among young people. Following his own case of the novel coronavirus, even Prime Minister Boris Johnson, known for criticizing government “nannying,” helped launch a campaign to reduce obesity in the U.K. “I was too fat,” he says in a video released this summer.
What is still emerging, however, is how widespread the link between obesity and severe responses to COVID-19 might be, the biological mechanisms at play and what all this means for those chasing new drugs and vaccines for the virus.
A new analysis of existing research on obesity and influenza, published in the journal Endocrinology this month, pinpoints one part of the immune system, the macrophage. According to co-author Durga Singer, of the University of Michigan, “Obesity causes a chronic, low grade activation of some parts of the immune system. When someone with this preexisting condition is faced with an infection, this could lead to hyper-activation of the immune system, but in a detrimental way that does not fight infection.”
Previous research has shown that even after vaccination, people living with obesity are more likely than those with a healthy Body Mass Index to develop the flu. This “dysregulation” of the immune system may in turn “drive organ injury in development of severe COVID-19,” according to the Michigan meta-study.
A report in Science by veteran journalist Meredith Wadman also notes that “fat in the abdomen pushes up on the diaphragm, causing that large muscle, which lies below the chest cavity, to impinge on the lungs and restrict airflow.”
In an interview with the magazine, Dr. Beverley Hunt, medical director of the British charity Thrombosis UK, adds that patients with obesity, already prone to blood clots, have “the stickiest blood I have ever seen in all my years of practice.”
According to the World Health Organization, rates of obesity have nearly tripled since 1975. In 2016, more than 1.6 billion people around the world were overweight (defined by a BMI equal to or greater than 25) and more than 650 million people were living with obesity (a BMI equal to or greater than 30). In Canada, 26.8 per cent of adults 18 and older, about 7.3 million people, are living with obesity.
In late August, the World Obesity Federation reported “an approximate doubling of risk of complications and mortality from COVID-19 among people with obesity,” based on research from China, the U.K., the US., France and Italy.
Morbid obesity, classified as a BMI of 40 or greater, increases grim outcomes. An article published by the The Journal of the American Medical Association Wednesday looked at more than 3,000 hospitalizations due to COVID-19. Among patients aged 18 to 34, nearly 24 had morbid obesity — 41 per cent of whom required ventilation or died.
If these are extreme cases, Naveed Sattar, a professor of cardiovascular and medical sciences at the University of Glasgow, says any weight in excess of healthy norms appears to impact COVID-19 responses. As he told Science, “BMI remains a strong independent risk factor … And it seems to be a linear line, straight up.”
That’s particularly bad news given experts’ worry that the pandemic is exacerbating existing obesity rates. During the early stages of lockdowns and shelter-in-place orders, food supply chains were strained, many people relied on packaged foods with a longer shelf life instead of fresh produce, and physical activity decreased.
For all this, there appears to be little consideration of obesity in the current race to develop new drugs and vaccines for the novel coronavirus. “To our knowledge none of the several thousand clinical studies of covid-19 in international clinical trial registries proactively recruit participants with obesity,” wrote three British endocrinologists in an open letter published in the BMJ. “On the contrary, several studies consider overweight or obesity as exclusion criteria.
“We call for proportional representation of people with obesity in clinical trials of drugs and vaccines, including dose finding studies.”
The World Obesity Federation has also issued a call to action for more serious responses to obesity amidst the pandemic, both from the WHO and member states.
One member wrote: “WHO does not explicitly include obesity in its guidance to countries, and this is part of the reason national governments do not prioritize it, even though it has been demonstrated to be one of the most serious drivers of COVID complications.”
Among the organization’s recommendations: countries should track the BMI of people who are hospitalized or die from COVID-19; advice for people living with obesity on how to protect themselves from the virus; and recommendations on how health professionals should tailor their care.
Don’t miss the latest on COVID-19, reopening and life. Subscribe to Healthing’s newsletter COVID Life for daily updates on the top health news and the Healthing Weekender delivered to your inbox on Saturday.