FGF21 and obesity due to melanocortin 4 receptor deficiency: Moreover, obesity induced by a high-fat diet alters the M1/M2 macrophage ratio and promotes tumor fibrosis through the upregulation of fibroblast growth factor 21 (FGF21), thereby diminishing the efficacy of standard chemotherapy treatments such as paclitaxel and carboplatin in murine models [47].