Obesity is a known risk factor for severe COVID-19 outcomes. Data on hospitalized patients in the U.S. showed that individuals with an obese body mass index (BMI) had an increased risk for death from COVID-19. The association for death was even more pronounced among adults less than 65 years old.

Obesity is also a risk factor for severe COVID-19 outcomes not limited to hospitalization, intensive care unit (ICU) admission, mechanical ventilation requirement, and mortality. In March 2021, the U.S. Centers for Disease Control and Prevention (CDC) reviewed data from the Premier Healthcare Database Special COVID-19 Release (PHD-SR). Across the U.S., 238 hospitals contributed data on 148,494 patients admitted for COVID-19 infection between March and December 2020. Patients with an obese BMI of 30-34.9 kg/m2 had 1.08 times the risk of death from COVID-19. Patients with an obese BMI of 45 kg/m2 or more had 1.61 times the risk. The association for death was even more pronounced among adults less than 65 years of age. Patients in this category with a BMI of 45 kg/m2 or more had 2.01 times the risk of death. 

More research is needed to better understand how obesity increases an individual’s risk of death and other severe outcomes from COVID-19. Experts speculate that the chronic inflammation present with obesity may weaken the immune system, making an individual more susceptible to infections. Excess weight may also impair lung function and contribute to worse outcomes.

Obesity is abnormal and excessive adiposity, or body fat. It is determined using body mass index (BMI), a crude marker of health status calculated by dividing a person’s weight (in kilograms) by the square of their height (in meters).

Though it is not a definitive diagnostic tool for health, BMI is used to inexpensively screen an individual’s risk for chronic diseases. Those with an overweight or obese BMI are at a higher risk of a poorer quality of life, all-cause mortality, and other diseases, including Type 2 diabetes, hypertension, coronary heart disease, osteoarthritis, and some cancers. 

Obesity is now recognized as a complex, chronic disease influenced by myriad and interconnected factors, like geographic location, socioeconomic status, educational background, ethnicity, diet, exercise, and family genetics. Obesity rates are also increasing across all age groups. In the United States, between 2017-2018, prevalence was highest among adults aged 40 to 59 years, followed by adults aged 30-39 years, and adults aged 60 years and over.