Coronavirus Disease 2019 (COVID-19) has claimed more than 1.25 million human lives since December 2019. Almost 50 million people have had a confirmed SARS-CoV-2 infection to date, the clinical spectrum of which ranges from symptomatic infection to severe COVID-19 with critical illness.

Obesity is a risk factor for worse outcomes in patients with COVID-19 and consequences can be life threatening as overweight people are more likely to be hospitalised, transferred to ICU (Intensive Care Unit) or even die than normal weight thinner people.

Data reveals that the risk of death from COVID-19 compared with the rest of the population increased by 40% for people with a BMI of 35 to 40kg/m2 and 90% with a BMI of over 40.

6 reasons why obesity is a risk factor for worst outcome in COVID infected patients are:

  • Hyperinflammation – Obesity is a state of enhanced chronic inflammation. Therefore, predisposition to systemic hyper-inflammation is believed to be one of the main mechanism by which obesity leads to  worse outcomes in COVID-19. Fat is an important endocrine organ, containing adipose tissue that produces hormones in response to other body organs. These are known as inflammatory markers. More the excessive body fat, higher will be the inflammatory markers in the person. Since the COVID-19 virus work to trigger an inflammatory response, often obese people will experience a much stronger and exaggerated inflammation.

  • Weakened immune function – Obesity itself has been shown to decrease immune function. Increased susceptibility to severe COVID-19 infection is hypothesised to be linked to impaired successful immune responses against the virus. Science has shown us that immune system is stronger when we follow a healthy diet and exercise moderately.

  • Escalated immune response – Cytokine storm is escalated immune response resulting in corona virus related fatalities. People with obesity are sensitive to infection and develop a more intense cytokine storm. According to NIH, National Cancer Institute, cytokine storm is defined as a severe immune reaction in which the body releases too many cytokines into the blood too quickly. Cytokines play an important role in normal immune responses, but having a large amount of them released in the body all at once can be very harmful.

  • Perturbed intestinal microbiota – Obesity is associated with a perturbed intestinal microbiota that otherwise would directly prevent the invasion of pathogens including COVID-19 virus. We know that the bacteria in the intestines are protective. They control digestion, hunger, metabolism  and also immunity. Any changes to the gut bacteria has an impact on our immunity and this noticed in people with COVID-19 infection.

  • Higher viral load – The receptor for virus that causes COVID-19 (SARS-CoV-2) is ACE2, a member of the angiotensin receptor family that has relatively large tissue distribution. The adipose fat tissue also expresses ACE2 suggesting adipocytes are potentially infected by SARS-CoV-2. The fact that ACE2 is also expressed in adipose tissue, mainly in visceral fat, suggests that severely obese individuals can host significantly higher viral load leading to local inflammation, thereby making this population (obese) more prone to develop severeCOVID-19 infection.

  • Reduced lung compliance – Accumulation of fat in and around the ribs and diaphragm and abdomen compress the lung resulting in impaired lung capacity in obesity. Obese people spend considerable energy to overcome the reduction in chest wall compliance (the elastic work). In addition, considerable energy is also spent to overcome the air-flow resistance (the non-elastic work). All these deleteriously affect the respiratory function. For these reasons the already compromised respiratory system in obese COVID-19 pneumonia patients struggle to recover.

    Francesco Rubino, chairman of metabolic and bariatric surgery at King’s College London has the final word, “The pandemic really brings to the fore the need to tackle obesity more aggressively. One lesson from the pandemic of COVID-19 is that not treating obesity is not an option.”

 

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Author:

Dr Nishant Ranjan, Consultant Diabetes & Endocrinology

Deputy Clinical Director- Urgent care & Medicine

Barnsley District General Hospital