Likewise in obesity, increased levels of SCFA acts as ligands for the free fatty acid receptors FFAR2 and FFAR3 (Kimura et al, 2020), which upon activation trigger the secretion of appetite and body weight regulating hormones such as leptin, glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2), and peptide YY (PYY), and cholecystokinin (CCK). Here, CCK is linked to obesity due to melanocortin 4 receptor deficiency.