Inhibitors of DPP-4 (the enzyme that deactivates GLP-1) and GLP-1 analogs that have functions similar to those of GLP-1 have been commercialized for the treatment of diabetes [12,38] and have also recently been used for the treatment of obesity [12,38,39,40]. This evidence concerns the gene GCG and obesity due to melanocortin 4 receptor deficiency.