We first characterized the expression of Cnr2 (encoding CB2) in the adipose tissue and in the liver, and its regulation overtime during obesity, using genetically obese leptin-deficient ob/ob mice and wild type (WT) C57Bl/6J mice fed a high fat diet (HFD) for 6 or 15 weeks. This evidence concerns the gene CNR2 and obesity due to melanocortin 4 receptor deficiency.