IGF1 and neoplasm: The mechanisms underlying the beneficial effects of fasting include the reduction in circulating IGF1 concentrations and the induction of autophagy in cancer cells (which favors the release of ATP for the recruitment of immune effectors into the tumor bed) as well as a favorable shift in the tumor microenvironment, with an increase in the ratio of CD8+ cytotoxic T lymphocytes over FOXP3+ regulatory T cells (refs. 5, 7, and Figure 1A).