In obesity and T2DM, several dysregulated systemic factors, such as insulin, insulin-like growth factor-1 (IGF-1), glucose, lipids, pro-inflammatory cytokines, adipokines, steroids, immune cells, the autonomic nervous system, and the gut microbiota, have been suggested as contributing factors for cancer initiation and progression [15]. Here, IGF1 is linked to obesity due to melanocortin 4 receptor deficiency.