Several recent studies reveal that obesity represents an important risk factor to result in the most serious clinical complications associated with severe forms of COVID-19.
According to recent estimates, 95 % of the people who died from COVID-19 had at least one underlying chronic disease, whether type 2 diabetes, heart or lung disease, or even cancer(1). Since the incidence of these diseases increases greatly over the course of aging, this explains in large part why older people are more at risk of dying from this disease, especially when they are already weakened and/or hospitalized at the time of the infection, such as in NURSING homes. This is not the age that is responsible for the vulnerability of older people, but the fact that their health is generally worse than in the rest of the population, because chronic diseases have had more time to express their adverse effects on health.
Obese at risk
As the pandemic progresses, however, it is increasingly evident that the advanced age is not the only risk factor to be seriously affected by the COVID-19. Several recent studies have reported, inter alia, that an unusually high proportion of patients admitted to hospital for more young people (60 years old) were overweight and that being overweight increases the risk of complications of the COVID-19. For example, a French study has shown that 85 % of patients with the disease who were treated in the icu were overweight, and that patients with a BMI > 35 kg/m2 (severe obesity) were seven times more likely to require mechanical ventilation than patients of normal weight(2).
In the United States, it has been observed that patients under the age of 60 years who were obese (BMI of 30-34 had a risk two times higher of being admitted to the intensive care unit compared to patients of normal weight, an increase in risk, which reached 4 times for the morbidly obese (BMI > 35)(3). The very high incidence of obesity in certain segments of the american population (almost 80% among african-american women, for example) could therefore explain the high proportion of cases of Covid-19 actually observed in these ethnic minorities.
Mechanical problems and metabolic
The first factor that explains this link between overweight and the severity of the Covid-19 is purely mechanical : the thoracic cage of obese patients is compressed by excess fat, which reduces the functional capacity of the lungs. The breathing may be more compromised by excess weight in the abdomen, which will impede the movement of the diaphragm, especially in the supine position. In other words, the lungs of obese people do not function optimally and are therefore more susceptible to lung infections. It should also be noted that this phenomenon involving overweight and viral infections is not restricted to the Covid-19, but has also been observed for respiratory tract infections caused by other viruses (influenza, H1N1, for example).
The second factor linking overweight and severity of the viral infection is biochemical. Obesity is an important risk factor for type 2 diabetes and metabolic syndrome, two conditions that increase 10 times the risk of dying from the Covid-19(4). This is most likely due to chronic inflammation caused by excess fat, which dysregulates the immune response directed against the virus causing production of excessive inflammatory cytokines. This phenomenon, called ” storm of cytokines, is now recognized to contribute to the rapid degradation of physiological functions (heart, kidney, brain) that is frequently observed in patients with severe forms of Covid-19 and which results in an increase unheard of death of patients intubated, to the intensive care unit.
We have mentioned several times, but it needs to be repeated : obesity is not a cosmetic issue, but an issue of overall health. Disordered metabolic that are associated with overweight disrupts the normal balance of physiological functions and make the body vulnerable not only to the development of several serious diseases (diabetes, cardiovascular diseases and cancer), but also the complications that arise from viral infections.
(1) Chow N, et al, Preliminary estimates of the prevalence of selected underlying health conditions among patients with coronavirus disease of 2019 — United States, February 12–March 28, 2020. MMWR Morb Mortal Wkly Rep 2020; 69: 382.
(2) Simonnet A et al. High prevalence of obesity in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) requiring invasive mechanical ventilation. Obesity, published April 9, 2020.
(3) Lighter J et al. Obesity in patients younger than 60 years is a risk factor for Covid-19 hospital admission. Clin. Infect Dis., published April 9, 2020.
(4) Bornstein SR et al. Endocrine and metabolic link to coronavirus infection. Nature Rev. Endocrinol., published April 2, 2020.