Several biological mechanisms may sustain the protective effects of cardiorespiratory fitness and muscle mass, including enhanced metabolic regulation, reduced circulating insulin and IGF-1, which are key drivers of cancer cell proliferation (Tsiani et al. 2021), increased release of myokines, such as SPARC, OSM, IL‐6, and IL‐15, which have a direct antitumor effect by inhibiting cancer cells’ growth (Bettariga et al. 2025; Kim et al. 2022, 2023). Here, IL15 is linked to cancer.