Although recent data indicate that obesity may increase the risk for severe COVID-19, more studies are needed on this association.

The study

This meta-analysis of 40 studies assessed the associations between obesity (BMI ≥30) and COVID-19 severity and comorbidity and also discussed the mechanisms involved.

The results

The meta-analysis found that obesity was associated with increased probability of poor outcome, invasive mechanical ventilation, and mortality, but it was not associated with ICU admission risk.

The authors identified several mechanisms by which obesity may increase the risk for severe COVID-19:

  • Fat deposits in the mediastinum and abdomen may impair respiratory system function, predisposing patients to hypoventilation-associated pneumonia, pulmonary hypertension, and cardiac stress.

  • Proinflammatory cytokines and adipokines (signaling molecules) released by fat cells may impair immune function.

  • Visceral adipose tissue can express high levels of angiotensin-converting enzyme 2 (ACE-2) receptors, which might bind SARS-CoV-2, potentially increasing the ability of the virus to spread within the body.

  • Obesity may increase the risk for vitamin D deficiency, which may increase susceptibility to severe COVID-19 symptoms.

  • Adipose tissue may act as a viral reservoir, increasing the duration of virus shedding.

  • Diagnosis based on pulmonary ultrasound may be more difficult to implement for patients with obesity, potentially preventing an early diagnosis.

  • Obesity can increase the risk for other comorbidities such as type 2 diabetes, kidney disease, and cardiovascular disease, further increasing the susceptibility to severe COVID-19.


Obesity has been identified as a risk factor for severe disease and death for many respiratory viruses. During the 2009 influenza A virus H1N1 pandemic, obesity was also associated with increased risk of severe disease and was a risk factor for hospitalization and death; similar associations were observed in the 1968 influenza epidemic. Therefore, COVID-19 infection is not that different from other respiratory viruses.

Also, obese patients with COVID-19 shed virus for up to twice as long as nonobese patients, and they tend to have poorer responses to vaccine as well.

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This Study Summary was published on April 4, 2021.