Background
On December 2019 a new coronavirus (SARS-CoV-2) emerged in Wuhan, China, triggering a pandemic of severe acute respiratory syndrome in humans (COVID-19) [1]. Today, the scientific community is investing all the resources available to find any therapy and prevention strategies to defeat COVID-19. At the beginning of this pandemic, it was difficult to identify COVID-19 risk factors, that can be targeted for disease prevention. Working on risk factors can, in fact, prevent infection and improve outcomes. Now it is well known that obesity represents a significant risk factor both for COVID-19 susceptibility and prognosis [2]. Applying immunonutrition to obese patients can also prevent hospitalization, representing an additional risk factor for worsening COVID-19 prognosis. Moreover, immunonutrition in obese patients may be a relevant strategy to lower the burden of COVID-19 disease [3], given that obesity affects almost 13% of people in the world [4]. The present umbrella review seeks to answer the question of whether a nutritional approach could be used to enhance the immune system’s response to obesity in patients affected by COVID-19, focusing on the interplay between immunonutrition, inflammation and gut microbiota.