Impact of obesity on COVID-19 diagnosis and outcomes

COVID-19 is caused by SARS-CoV-2 viral infection of the respiratory tract. Whilst most people recover from the disease, approximately 3.6% of people die from COVID-19.¹ Mortality from COVID-19 is a greater risk for people with certain risk factors such as being male, black ethnicity, older age, specific chronic health conditions or obesity.²³⁴⁵⁶⁷

Since this virus infects the respiratory tract, it’s somewhat surprising that being a smoker or having chronic respiratory conditions, such as chronic obstructive pulmonary disease, are not particularly strong risk factors for COVID-19 infection or outcomes.⁷⁸

Many studies have concluded that obesity is a risk factor for COVID-19 disease severity.^691011121314

Numerous meta-analyses have combined data from multiple studies, consistently finding that people who are obese have a higher risk of:

• hospitalisation^{24 5 6}
• intensive care use²³⁵⁶
• mechanical ventilation³⁵⁶ and
• mortality²³⁴⁵⁶

from COVID-19, compared to people in the healthy weight range. People who died from COVID-19 were about 1.5 times more likely to be obese, with BMI over 30 kg/m².^{2 3} These associations remained when demographic factors such as age, sex and socioeconomic status were taken into account.

A large prospective study that closely examined the interactions between different clinical risk factors for COVID-19 mortality showed that having cardiovascular disease, hypertension, diabetes, autoimmune disease or oral steroid use were independently associated with COVID-19 mortality.⁷ Obesity was not independently associated with mortality in this study. These results indicate that the increased COVID-19 mortality risk from being obese may be due to conditions caused by obesity, such as cardiovascular disease and diabetes.⁷

People who are living with obesity may be more likely to be diagnosed with COVID-19 compared to people in a healthy weight range.²¹⁵¹⁶ Prospective studies from the United Kingdom used pre-existing data from primary care databases and biobanks to show that people with obesity were more likely to test positive for COVID-19.¹⁵¹⁶ These studies have predicted a 1.41 to 1.55 fold increase in the odds of testing positive for COVID-19 for people with obesity compared to those in the healthy weight range. The biological mechanisms underlying this observation are currently under investigation.

Statements by the World Health Organization and the World Obesity Federation support the association of obesity with poor outcomes from COVID-19. The World Health Organisation has stated that:¹⁷

“The latest scientific evidence, based on multiple studies, shows that patients with obesity (including young adults) hospitalized with COVID-19 experienced substantially higher rates of severe outcomes, such as requiring intensive care treatment, mechanical ventilation and death.”

The World Obesity Federation has stated that:¹⁸

“Systematic reviews and meta-analyses overwhelmingly show that obesity is associated both with a higher risk for intensive care unit (ICU) admission and poorer outcomes for COVID-19.”