Highlights Fasting mimicking diet induces prenatal-development gene expression in adult pancreas FMD promotes Ngn3 expression to generate insulin-producing β cells Cycles of FMD reverse β-cell failure and rescue mice from T1D and T2D Inhibition of PKA or mTOR promotes Ngn3-driven β-cell regeneration in human T1D islets Summary Stem-cell-based therapies can potentially reverse organ dysfunction and...