Can weight loss help protect against Covid-19?

By Jen Christensen, CNN

In the holiday season, when the average American can easily pack on a few pounds, experts say there is another reason to pay attention to your weight: Covid-19.

People who are overweight or obese are at a much higher risk of much more severe disease and even death from Covid-19, and one new study suggests that losing weight can reduce that risk.

The obesity epidemic has been a threat to Americans’ health for years. It’s the second leading cause of preventable death, after smoking. With Covid-19, it becomes even more dangerous. One study found that 30% of Covid-19 hospitalizations were in people with obesity.

The obesity clinic where Dr. Fatima Cody Stanford works in Boston has a 1,000-plus person wait list that grew a lot longer with the pandemic. Even with more than a dozen specialists on staff, it’s not enough to meet the demand.

“We are overwhelmed with the volume of patients that have really made that connection between obesity and Covid and the need for them to get appropriate care,” said Cody Stanford, who is also an assistant professor at Harvard Medical School.

Obesity and the increased risk of Covid-19

People with obesity are 46% more at risk of getting Covid-19, according to a study from August. It found that they are also more at risk of getting really sick, facing a 113% higher chance of being hospitalized, a 74% higher risk of needing to be treated in the ICU and — perhaps most troubling of all — a 48% increased risk of death.

“The risk goes up and up and up with each increase” in body mass index (BMI), said study co-author Barry Popkin, a distinguished professor in the Department of Nutrition at the University of North Carolina Gillings School of Global Public Health.

Dozens of studies have shown similar results.

Research from the US Centers for Disease Control and Prevention also found that those with the lowest risks of Covid-19 severity had BMIs near the threshold between healthy weight and overweight in most instances, and the risk went up with higher BMI.

Another study that looked at records from more than 6.9 million people in the UK found a direct increase in the risk of severe Covid-19 leading to admission to hospital and death in people at the top of what’s considered a healthy BMI; it increased with more weight.

Does losing weight reduce Covid-19 risk?

The increased risk has led many to wonder if losing weight might keep them from catching or getting sicker with Covid-19.

Ethically, it would be nearly impossible to do randomized controlled trials to determine this, according to Dr. David Kass, a cardiologist at Johns Hopkins Medicine. But scientists have seen how weight loss can help in trials for other diseases with similar problems.

“There’s no question, in controlled trials with people who are obese and have heart failure, that if they go through a weight reduction or an exercise program or a combination, and we look at this marker of how they are doing, the answers to that are yes, there is evidence that weight loss is a good thing,” Kass said.

A large retrospective study published last week in JAMA Surgery suggests that substantial weight loss makes a difference.

The study, looking at records from 20,212 people for more than six years, was funded by a grant from Medtronic, which makes devices for weight loss surgery.

The rates of positive Covid-19 tests were similar in the surgical and control groups: 9.1% and 8.7%, respectively. The weight loss among the group that had surgery was associated with a lower risk of hospitalization, need for supplemental oxygen and severe symptoms from a Covid-19 infection. This patient group also had a 53% lower 10-year cumulative incidence of all-cause non-Covid mortality, compared with the control group.

“The findings suggest that obesity can be a modifiable risk factor for the severity of Covid-19 infection,” the study said.

Dr. Steven Nissen, a cardiologist with Cleveland Clinic who co-authored the study, said it’s important to understand that weight loss is the key with this study, not the surgery itself.

The surgery just happens to be an effective way to lose weight.

“Losing weight is completely reversible,” Nissen said. “As far as we can tell, if you lose weight, then your risk of serious Covid and Covid morbidity and mortality goes way down.”

Why obesity is a threat

Obesity is a problem with Covid-19 for a variety of biological reasons.

“Fat cells are living cells, and as soon as you start to accumulate them, they’re essentially impacting your immune system negatively,” Popkin said. “From the word go, they’re inflamed.”

Fat cells create chronic inflammation. With obesity, blood is also prone to clot, the big mass of tissue below the diaphragm makes the heart work harder, and the fat in the abdomen and liver puts out cytokine chemicals that cause tissue damage and additional vascular issues, all of which can make Covid-19 much more severe.

People with obesity also don’t breathe as easily as people with healthier weight; they can carry excess weight on the thorax that can compress the lungs so they cannot completely fill with air. So people with obesity take shallower breaths, and the actual space where oxygenation is happening is smaller.

“It’s like when you’re lying down and breathing, and if I sat on top of your chest and you tried to breathe. It is much harder to catch your breath when your lungs are smashed,” said Dr. Rekha Kumar, an obesity medicine specialist and an associate professor of clinical medicine and attending endocrinologist at Weill Cornell Medical College. “If you’re starting with a compromised respiratory system and this is a respiratory disease, you’re already at a disadvantage.”

The importance of taking obesity seriously

Experts say the problems that obesity brings in this pandemic have been significantly underestimated.

“There’s not a country in the world that has less than 20% of adults with obesity,” Popkin said.

Covid-19 death rates are 10 times higher in countries where most adults are overweight, a report in March found.

The US has one of the highest rates of obesity in the world, at more than 42% of the adult population, according to the CDC. And that’s probably a conservative number, because those statistics come from 2018. More than 73% of adults are considered overweight. And while the numbers aren’t as high for children, more than 20% of those 6 to 19 have obesity, and more than 13% of children 2 to 5 do.

“I think people don’t see obesity as the disease that it is. They think of it as a lifestyle choice,” Cody Stanford said. “A lot of people think those people just need to eat less and exercise more, but if that mantra worked, we wouldn’t have the prevalence of obesity that we have now.”

So what should people do?

Cody Stanford said she tells her patients not to focus on losing a certain number of pounds. Instead, they should be thinking in terms of inches. She’ll even give a target waist circumference: less than 35 inches in women and less than 40 inches in men.

Obesity is not just about weight or BMI, it’s about where that weight is distributed.

Generally, abdominal fat is one of the most dangerous kinds. The fat in the stomach area grows deep inside the body and wraps around vital organs. The liver borrows this fat and turns it into cholesterol that can sneak into the arteries and start collecting there. When that happens, the arteries start to harden, and this can lead to a heart attack or stroke.

This deep layer of belly fat is also what makes the body insulin-resistant and keeps it in a constant state of chronic inflammation. “When you add the inflammation of Covid on top of it, it can increase the risk of severe illness,” Kumar said.

A better central distribution of weight is key, she said.

“If that were better, they would likely have fewer complications from Covid and fewer deaths,” Cody Stanford said. “Just looking at the weight in and of itself without looking at the whole picture would be a flawed way of thinking of it.”

Based on studies of other diseases, Popkin says, even a person who is overweight but loses 5 pounds can see improvement in their diabetes and hypertension.

“Any weight loss is a positive at nearly any weight level,” he said. “Just marginal weight gain can impact us health-wise.”

Popkin added that weight loss is not nearly as protective as a vaccine or a booster.

“But certainly, it will have some benefit,” he said — especially coming out of the holiday season.

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