Glucagon-like peptide-1 (GLP-1), a strong regulator of insulin secretion and appetite (Müller et al., 2019), has been successfully harnessed for the treatment of type 2 diabetes and obesity (Holst, 2020), and a number of drugs linking GLP-1-based peptides with other hormones are in the pipeline, potentially offering superior clinical efficacy with reduced side effects (Capozzi et al., 2018; Frias et al., 2018; Parker et al., 2020). Here, GCG is linked to obesity due to melanocortin 4 receptor deficiency.