In the early days of the COVID-19 pandemic, some of America's leaderswondered aloudif the cure for the virus — restrictions like business shutdowns, mask mandates and social distancing — might be worse than the illness itself, which has led to more than 500,000 deaths in America alone.

Those leaders advocated for broad reopening so that the population could reach something called herd immunity — essentially, focusing mitigation efforts on the elderly population and people with chronic disease who were at a high risk for severe illness or death, while letting others get COVID-19 and build antibodies among the general population.

But Dr. David Ludwig, an endocrinologist at Boston Children’s Hospital, told Boston Public Radio on Friday that that plan would have put many Americans in direct risk, because of an epidemic that pre-dates the pandemic: obesity rates.

According to the CDC, more than 40 percent of Americans are overweight or obese, and those people account for more than 75 percent of people who have been hospitalized, needed a ventilator or died from COVID-19.

"Obesity in general, and specifically metabolic dysfunction — conditions like insulin resistance that goes along with obesity — would predispose the American population uniquely to both getting COVID and suffering severe and potentially fatal COVID, and that seems to have been born out," Ludwig said.

Behind advanced age, Ludwig said obesity and metabolic dysfunction are the next most important risk factors for COVID-19 severity.

Ludwig acknowledged thatmany people have gained weight this year, due in part to stress and long periods of inactivity, and urged people to be gentle with themselves.

"This has been a terrible year," he said. "If we gained weight, like the majority of the population... Congratulations on making it through this terrible year."

But, Ludwig said, that's also all the more reason to start talking more about weight, and how it factors into health. As more people become vaccinated, Ludwig said it's time to start focusing on the chronic problem that existed before COVID-19.

"It's not just about body weight, it's about maintaining our metabolism, our immunity, our resistance, which we all know is a factor in who gets sick and who gets healthy," he said.

Ludwig said the issue partially lies within our diets, which have been saturated by processed carbohydrates "that flooded the diet and continue to do so since the low-fat years." These are things like sugary beverages, processed grain and potato products, said Ludwig.

"Step one, start to reduce those [types of food], but we don't want to add deprivation at the same time," he said, advocating for adding "healthy, luscious high fat foods" like nut butters, high fat dairy, full fat dairy, avocados, and dark chocolate.

Ludwig said these foods improve metabolic function "regardless of weight."

Dr. Ludwig is a practicing endocrinologist and researcher at Boston Children’s Hospital. He is also professor of pediatrics at Harvard Medical School and professor of nutrition at Harvard School of Public Health.