On the other hand, CRC patients with obesity (OB-CRC) display a specific gut microbiota profile characterized by a reduction in butyrate-producing bacteria and an overabundance of opportunistic pathogens, which in turn could be responsible, at least in part, for the higher levels of proinflammatory cytokine IL-1β, the deleterious bacterial metabolite TMAO, and gut permeability found in these patients (33). Here, IL1B is linked to obesity due to melanocortin 4 receptor deficiency.