Recent studies have reported that the probiotic commensal bacteria strain Hafnia alvei (H. alvei), which produces the satietogenic peptide Casein-Like Protease B (ClpB), which mimics the effect of α-MSH, a key anorexigenic peptide involved in the regulation of appetite that stimulates in turn the release of PYY, reduces weight gain and adiposity in mouse models of obesity. The gene discussed is CLPB; the disease is obesity due to melanocortin 4 receptor deficiency.