ACE2 and obesity due to melanocortin 4 receptor deficiency: Obesity is highly related to both a more severe course of the acute phase and a higher risk of developing Long COVID, partly due to a systemic inflammatory state, proven by a higher level of pro-inflammatory cytokines, including IL-6 and TNF-a, and partly because of the endothelial dysfunction and the increased expression of ACE2 associated with being overweight [24,25].