What COVID-19 revealed about obesity and our immune system


The COVID-19 pandemic revealed much about the nation’s collective health. One issue it illuminated was the snowballing physiological effects of obesity.

UCLA Health’s Zhaoping Li, MD, and Vijaya Surampudi, MD, addressed the challenges in a newly published medical review exploring studies out of New York that identifies obesity as the second-highest risk factor – behind age – for severe disease and death from COVID-19.

“This pandemic has highlighted an underlying epidemic that we really have to deal with in the United States and that is obesity,” said Dr. Surampudi, an assistant professor of medicine in the Division of Human Nutrition. “Having extra weight on the body puts our body on high alert because it’s already inflamed.”

In the article, Dr. Surampudi and Dr. Li, professor of medicine and chief of the Division of Clinical Nutrition, explained how COVID-19 was initially perceived as a lung infection because it entered the lungs, replicated virally and caused inflammation.

Hospitalization and mortality data linked many of the serious COVID-19 infections to obesity and diabetes characteristics, which include a reduction in lung compliance (lungs become stiff) and a reduction in lung volume. Dr. Surampudi explained how obesity could further complicate lung functions of those diagnosed with COVID-19.

“When people have extra weight around the abdominal area, it can affect how much the lung can expand. There’s a lot more airway resistance and it also affects the chest expansion.”

Dr. Surampudi explained that obesity causes ventilation-perfusion mismatch – a scenario in which one or more areas of the lung receives oxygen but no blood flow, or receives blood flow with no oxygen. When this occurs, the person does not breathe properly.

Many researchers believe that people with COVID-19 who are not able to breathe well due to obesity are at more risk for severe complications.

Obesity and respiratory correlations in COVID-19 patients

Dr. Vijaya Surampudi, MD

In their review, Dr. Li and Dr. Surampudi cited one study that tracked 393 patients diagnosed with COVID-19. Obesity was the primary risk factor among the patients that required mechanical ventilation. It was also discovered that respiratory failure was more common among patients that were classified as obese.

Many of the obese COVID-19 patients also suffered from what is known as acute respiratory distress syndrome (ARDS).

In another study, Dr. Li and Dr. Surampudi referenced in their paper, some COVID-19 patients with ARDS experienced multiple organ failure and eventually died.

Dr. Surampudi described how obesity affects the immune system when it comes to fighting infections such as COVID-19.

“If you think about a thermostat and you’re at a comfortable 70 degrees, then you turn it up to 75 degrees – that’s sort of what’s happening when there’s extra weight in the body. The body becomes a little uncomfortable and the immune cells are not at their optimum, nor are they functioning the same as when the thermostat was at 70 degrees.”

Similarly, obesity dampens the strength of the immune system and can expose the body to severe COVID-19 infections.

Measuring overweight and obesity

Dr. Zhaoping Li,

There are different levels of obesity, which experts consider to be accurately identified by body mass index (BMI) – a measure of body fat based on a person’s height and weight.

Dr. Surampudi said BMI does provide a sense of a person’s health, but she and her team look at overall body composition and body fat percentage to determine whether someone is at risk of health complications.

The standard BMI scale:

  • BMI 25.0-29.9 (overweight, but not obese)
  • BMI 30.0-34.9 (class 1 obesity)
  • BMI 35.0-39.9 (class 2 obesity)
  • BMI 40.0 and higher (class 3 obesity)

Weight gain more common during the pandemic

During the COVID-19 pandemic, many people put on weight and developed bad eating habits and a loosening of fitness regimens.

“We feel like we lost something,” Dr. Surampudi said. “We feel like we lost control, but there are things we can control like eating nutritious foods to optimize our immune system.”

Dr. Surampudi stressed that obesity can be caused by over-eating, medications, pre-existing health conditions, steroids, antidepressants and other factors. Exercise and diet not only can improve weight but also can improve immune system functioning and lower risk for severe disease.

“There’s been data showing that people who do moderate exercises seem to have lower risks of respiratory infection. Moving regularly helps our immune system,” she said.

“Also, throughout the week we want to be eating a good variety of vegetables, fruits, whole grains and adequate proteins just to make sure we’re getting all the nutrients our body needs.”