Lipopolysaccharide (LPS) is a membrane component of gram-negative bacteria such as Bacteroidetes and Proteobacteria that induces chronic low-grade inflammation, promoting obesity and IR through the activation of TLRs, mainly TLR4.54,55 Studies found that mice fed a 4-week high-fat diet had increased levels of circulatory LPS, promoting inflammation in adipose tissue due to potential diabetogenic proinflammatory cytokines (i.e. IL-1, IL-6 and TNF-α), weight gain, and liver IR.56 Here, IL1B is linked to obesity due to melanocortin 4 receptor deficiency.