The presence of human CYP2B6 in Cyp2b-null mice (hCYP2B6-Tg) reduced obesity in the females; however suprisingly, human CYP2B6 increased steatosis in association with several oxylipins including 9-HODE and 13-KODE from linoleic acid, and 12,13-DHET, 14,15-EET, and 14,15-DHET from arachidonic acid [8]. Here, CYP2B6 is linked to obesity due to melanocortin 4 receptor deficiency.