The world has been subjected to an unprecedented lockdown due to the coronavirus (COVID-19) pandemic caused by SARS-CoV-2.

COVID-19 has killed more people than its predecessors, SARS-CoV and MERS-CoV - the respective causes of severe acute respiratory syndrome (SARS) and the Middle East Respiratory Syndrome (MERS) - combined, despite SARS-CoV-2 having a lower fatality rate. 

This is because it spreads much faster among individuals, resulting in a high number of people infected in a short time. A person can easily become infected through respiratory droplets containing the virus, or by touching contaminated objects and surfaces. 

Initially, SARS-CoV-2 infects the cell of the respiratory system and causes severe inflammation and cell death. The virus subsequently infects and damages other vital organs and tissues, causing several complications that might affect the heart, the kidney, and the brain. 

Obesity: a risk of severe COVID-19 illness

Obesity is the excess of total body fat, defined by a body mass index (BMI) of 30 or higher. BMI is calculated by dividing the body weight in kilograms by the height in square meters (kg/m2). A person with a healthy weight has a BMI between 18 and 25 kg/m2, while a BMI between 25 and 30 indicates the person is overweight. 

Obesity poses a significant health threat, dramatically raising the risk of other diseases, including diabetes, heart disease, high blood pressure, fatty liver disease, dementia, stroke, and many cancers.

Recent studies from around the world have shown that, among patients admitted to intensive care with COVID-19, 40-45% were obese, requiring invasive mechanical ventilation. A new study conducted in the UK also concluded that obesity increases the risk of dying of coronavirus by 37%.

Obesity is now considered a risk factor for a more severe form of COVID-19, and possibly a risk of death, regardless of other illnesses. To date, the precise reason why obesity is associated with a more dangerous form of COVID-19 remains unclear. However, it is well established that obesity weakens the overall immune defense.

Furthermore, experts believe that severe COVID-19 in obese patients might be attributable to impaired lung function. Obese patients are more likely to have higher resistance in their airways, lower respiratory muscles, and lower lung volumes. Such factors increase the risk of lung infections (pneumonia) with bacteria, viruses, and fungi. 

Recent studies also indicate there is a higher risk of severe COVID-19 disease and death in people with diabetes and high blood pressure, two conditions that are linked to obesity. Uncontrolled blood sugar levels in diabetes weaken the immune system defenses and therefore increase the severity of infections and maybe the risk of death. 

As for hypertension, the reason why patients with high blood pressure are at risk of severe COVID-19, and even death, is not well understood. A combination of hypertension with aging in many COVID-19 patients is a suggested explanation. This combination makes the immune system less able to fight off the virus.

One unconfirmed theory suggests that certain medications used to treat hypertension increase the risk of severe COVID-19. These drugs increase the levels of a protein called ACE2 in the body. The SARS-CoV-2 virus must attach to the ACE2 molecule in order to infect cells. 
Even before COVID-19, the severity and incidence of infections are generally higher in obese individuals. 

Obesity epidemic: time for prevention

According to 2016 data from the World Health Organization, the number of people with obesity has reached 650 million individuals worldwide, and was linked to 4.7 million deaths globally in 2017. 

In several countries, approximately 60-80% of adults and 20-30% of children are now overweight or obese, the Middle East is one of the worst-hit areas. In Qatar, for example, 43% of adults are obese, almost double the global average rate. Worryingly, about 40% of Qatari students aged 5-19 are overweight suggesting that urgent measures are necessary to prevent childhood obesity from persisting into adulthood.

Obesity is a complex condition involving genes and environmental factors. However, the abundance of foods and drinks rich in calories, along with physical inactivity, are considered the primary cause of the obesity epidemic in the Middle East in general.

It is interesting, however, to note that, despite the high prevalence of obesity and diabetes in the Middle East, the mortality among COVID-19 patients is much lower than in some Western countries with lower obesity rates. 

Further research is needed to better understand the observed low COVID-19 mortality in the Middle East. Nevertheless, beyond the COVID-19 pandemic, and given the many life-threatening conditions linked to obesity, including more severe infections, there is an urgency to develop strategies to curb this rampant epidemic. 

The fight against obesity will succeed only with the sustained commitment of government authorities and private stakeholders, including families, schools, workplaces, food industries, sport organizations, and communities among others. 

Research and development are crucial for understanding the causes of obesity and ultimately identifying potential medications or other strategies against it. At Qatar Biomedical Research Institute, part of Hamad Bin Khalifa University, researchers are involved in projects to understand the genetics of obesity and to identify clues to predict and ultimately prevent the occurrence of obesity in the first place. 

* Dr. Abdelilah Arredouani is a scientist working in the Diabetes Research Center at Qatar Biomedical Research Institute, part of Hamad Bin Khalifa University.