The relationship between obesity and SARS-CoV-2 coronavirus infection

Obesity is a chronic disease centred on adipose tissue, which causes multiple other diseases, such as metabolic (type 2 diabetes mellitus, arterial hypertension, dyslipidemia), cardiovascular (coronary heart disease, heart attack, stroke) and other serious conditions such as knee osteoarthritis, sleep apnoea, fatty liver infiltration and some cancers. In Greece, obesity has been increasing steadily over the last 30 years and now more than 25% of adults and 14% of children are considered obese.

SARS-CoV-2 coronavirus infection includes a wide spectrum of pathogenesis ranging from simple asymptomatic infection or mild symptoms, such as fever, cough, sore throat, to more severe symptoms, such as dyspnoea, severe pneumonia, acute respiratory syndrome, pulmonary fibrosis and sometimes death. The infection has reached pandemic proportions, according to the World Health Organization, causing hundreds of thousands of deaths in some countries.

With regard to obesity, there is strong evidence that obesity is a serious - if not the most serious - risk factor for Covid-19 infection and therefore obese people are a particularly vulnerable group.

Here is some recent evidence in the form of questionnaires on the relationship between obesity and coronavirus.

Does obesity increase the risk of SARS-CoV-2 infection?

It is not yet fully established that obesity itself is a risk factor for contracting this virus. However, it is suspected that its coexistence with other risk factors, such as diabetes, arterial hypertension or cardiovascular disease, creates a favourable environment for coronavirus infection. Data from other viral infections (e.g. influenza type A) show that obesity, due to modification of the immune response and induction of lymphopenia, but also due to a longer duration of viral load carriage, predisposes to viral infections.

Is an obese person at risk of becoming seriously ill from COVID-19?

The answer comes from studies of hospitalized patients in France, China and the United States and unfortunately it is positive. Indeed, obese people have more severe symptoms, such as shortness of breath, are hospitalised more often and for longer days, are more often admitted to intensive care with the need to use a ventilator and probably have a higher mortality rate. 3 out of 4 Americans hospitalized for coronavirus infection are obese. In a study of 4000 coronavirus sufferers in New York, it was found that the main reasons for hospital admission due to infection were age over 65 and obesity itself, with secondary risk factors being hypertension, diabetes and cardiovascular disease. Also, although young people are generally a low risk group for this virus, when they are obese they become more and more severely ill. More than 80% of younger patients (under 50 years of age) admitted to intensive care units in France are obese.

In addition to obesity, other aggravating factors found to be associated with COVID-19 severity and long-term hospitalization are hypertension, diabetes, metabolic syndrome, cardiovascular and chronic respiratory diseases. At least one of the above-mentioned conditions was found in 91.5% of those hospitalized in the United States from COVID-19. Epidemiological studies in America show that areas with very high rates of obesity, such as New Orleans and Louisiana, have much higher mortality due to coronavirus than areas with less obesity, such as New York and Seattle. We consider ourselves lucky in Greece that there has not been a large spread of the pandemic, because with the high rates of obesity in our country, contracting the virus could be very serious.

Are there body mass index thresholds above which we face a higher risk from coronavirus?

Studies show that severe or morbid obesity (BMI over 40), which is accompanied by multiple morbidities, has more severe symptoms and increases the likelihood of prolonged hospitalisation. Individuals with such obesity are more susceptible to infections and experience more complications in the intensive care unit. Also, an important factor that complicates medical work is the difficulty of such patients to undergo diagnostic tests, e.g. blood tests, MRI. In addition, the treatment of these patients in the ICU presents particular therapeutic problems, such as difficulties in intubation, increased dosage of drugs, difficult therapeutic manipulations, and the need for increased nursing care. Another group of very high-risk obese patients are those who have undergone obesity surgery. These people are often deficient in proteins, minerals and vitamins and, having a weak immune system, are prone to infections.

The latest data show that even with simple obesity (BMI over 30) there is at least twice the risk of becoming more seriously ill.

What are the main reasons that put an obese person at risk for infection and how is this phenomenon explained scientifically?

In general, morbid obesity is often accompanied by pathological conditions such as hypertension, prediabetes or type 2 diabetes mellitus, renal or liver disorders (such as fatty liver infiltration and cholelithiasis), varicose veins and venous insufficiency of the lower limbs, skin fungal infections, vitamin deficiencies such as vitamin D, etc. These conditions are also common in simple obesity, especially when there is a large accumulation of fat in the abdomen (abdominal or male-type obesity). However, the respiratory problems often experienced by obese people prove to be particularly aggravating when they coexist with COVID-19. Such problems, such as dyspnoea on exertion, asthma, sleep apnoea syndrome and especially restrictive respiratory failure, reduce respiratory reserve and oxygenation and create conditions for infections.

Other mechanisms that are aggravating in obesity are the hyperinflammatory state, which predisposes to infections, the reduced resistance of the immune mechanism that is observed, and the adipose tissue itself can act as a storage space and a springboard for the promotion of the virus to other organs.

The risk that obese people are at risk of contracting the virus may motivate them to realise the magnitude of the problem and take it more seriously. Proper diet and exercise can help not only in weight loss, but also in immediate protection against the virus thanks to their anti-inflammatory action.

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