Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the novel coronavirus disease 2019 (COVID-19). The principal risk factor for the development of serious forms of COVID-19 was found to be the precarious metabolic health. There are several mechanisms that are implicated in the seriousness of COVID-19 ranging from attenuation of immune system function to chronic inflammation. It is important to keep in mind that obesity is a complex disease when discussing the relation between obesity and the severity of COVID-19. An increasing body of proof links obesity to COVID-19. Obesity has an obvious role in the high incidence, symptoms severity and mortality rates of viral infections seen in obese patients. Adipose tissue shows a high expression of the angiotensin-converting enzyme 2 (ACE2), the receptor for entry of SARS-CoV-2 into host cells, so obese population exhibit higher vulnerability to COVID-19. The primary immune response is offered mainly by type-I interferon (IFN-I) that is suppressed in COVID-19. The pro-inflammatory state associated with obesity produces imbalance of the inflammatory response to COVID-19, as the cytokine storm found in subjects with serious disease form. Obesity is considered as chronic inflammation of low degree, so it shows a capacity for pathogenic immune amplification. In this review, the effect of obesity on the immune system is described. The authors described the dysfunctional immune responses caused by obesity that lead to organ injury in COVID-19 infection and impair the ability of patient to combat the virus. Further research is required to assess the impact of obesity control, immunonutrition and physical exercise in SARS-CoV-2 infection.