The recognised role of hyperglucagonaemia in the pathophysiology of diabetes, and the effectiveness of concomitant activation of GCGR, alongside GLP-1R by oxyntomodulin, raises an apparently conflicting question: can glucagon antagonists or glucagon agonists be utilised as a diabetes or obesity therapy? This evidence concerns the gene GCGR and obesity due to melanocortin 4 receptor deficiency.