Obesity leads to severe COVID outcomes, even in young adults

If you are looking for inspiration to lose weight, here are two new, large studies from England and Mexico that show obesity is a strong risk factor for poor COVID-19–related outcomes, including death.

Hospitalization, ICU admission

In the first study, published in The Lancet Diabetes & Endocrinology, University of Oxford researchers extracted data from the QResearch database for nearly 7 million English patients 20 years and older with available body mass index (BMI) values registered at an eligible general practice from Jan 24 to Apr 30, 2020. It is the largest study to date assessing body weight and COVID outcomes.

Starting at 23 kg/m2, BMI was associated with coronavirus-related hospitalization (adjusted hazard ratio [aHR], 1.05) and, starting at 28 kg/m2, death (aHR, 1.04). There was a linear association across the entire BMI range for ICU admission (aHR, 1.10). 

According to the US Centers for Disease Control and Prevention, a BMI of 23 mg/k2 is considered normal, but 28 kg/m2 is considered overweight. The researchers found a significant link between BMI and age, with higher HRs for hospitalization above a BMI of 23 kg/m2 for patients 20 to 39 years old (aHR, 1.09), compared with no association for those 80 to 100 (aHR, 1.01). Similarly, Black patients had a higher risk of hospitalization than White patients (aHR, 1.07 vs 1.04).

The authors noted that even a small increase in BMI over 23 kg/m2 increased the risk of poor COVID-19 outcomes. These new data add to the overwhelming evidence that support excess body weight are an important, causal risk factor for more severe COVID-19 outcomes. 

Obesity alone, in combination with other comorbidities

The second study, published in Epidemiology & Infection, was led by researchers at the Instituto Nacional de Ciencias Medicas y Nutricion and the Instituto Nacional de Cardiologia Ignacio Chavez in Mexico City. 

The national observational study involved analyzing data from 15,529 COVID-19 inpatients and outpatients in Mexico’s 32 states from the National COVID-19 Epidemiological Surveillance Study between Feb 24 and Apr 26, 2020.

The case-fatality rate was 9.2%, and 21% of hospitalized patients died. Obesity alone almost tripled the risk of death (aHR, 2.7), while obesity combined with other underlying illnesses increased the risk of death and other severe outcomes even further (diabetes HR, 2.79; immunosuppression HR, 5.06; high blood pressure HR, 2.30).

The authors observed that Mexicans are metabolically distinct from Asians and Europeans in that they are more likely to have early-onset overweight or obesity. In addition, overeating, especially of highly processed foods, has led to an obesity epidemic in Mexico in recent decades, with 75.2% of the population older than 20 years either overweight (39.1%) or obese (36.1%).

Of all underlying illnesses, obesity was most strongly tied to COVID-19 infection in Mexicans with mostly symptomatic illness. Obesity alone and in combination with other comorbidities was a significant risk factor for secondary outcomes (pneumonia, hospitalization, [invasive mechanical ventilation], and ICU admission) in patients positive for SARS-CoV-2. Furthermore, the risk conferred by obesity increases when it is present alongside other comorbidities, particularly, [diabetes], hypertension, and immunosuppression.


Dr. Melvin Sanicas (@Vaccinologist) is a physician-scientist specializing in vaccines, infectious diseases, and global health.

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