GCG and obesity due to melanocortin 4 receptor deficiency: We previously reported that mice deficient in proglucagon-derived peptides (PGDPs), including Gcg, GLP-1, and GLP-2 (GCGKO), show resistance to obesity during 15 weeks of HFD feeding due to the increased expression levels of Ucp1 (uncoupling protein 1), which is involved in heat production in white adipose tissue (WAT) and brown adipose tissue (BAT) [27].