Several mechanisms of gut microbiota acting on the glycolipid metabolism of the host have been revealed, for example, bile acids (BAs) that are modified by the gut microbiota, serving as signaling molecules to target farnesoid X receptor (FXR) and G protein-coupled bile acid receptor-1 (TGR5), were found to promote the secretion of glucagon-like peptide-1 (GLP-1) to maintain glucose homeostasis (5), induce thermogenic genes and inhibit lipogenic genes to inhibit obesity (6). This evidence concerns the gene GCG and obesity due to melanocortin 4 receptor deficiency.