Resilience and restoration from fasting-refeeding mediated by a nutrient-regulated linker histone

Intermittent fasting and fasting-refeeding regimens can slow biological aging across taxa1. Shifts between fed and fasted states activate ancient nutrient-sensing pathways which alter cellular and epigenetic states to promote longevity2-4. Yet how biological age trajectories progress during fasting-refeeding, and how nutrient-sensing pathways reprogram epigenetic state remain largely unknown. Here we observe increases in predicted biological age of Caenorhabditis elegans during prolonged fasting in adult reproductive diapause, followed by extraordinary reduction of biological age during refeeding. We identify hil-1/H1-0 as an evolutionarily conserved nutrient-regulated linker histone which mediates adaptations to fasting and refeeding downstream of FOXO and TFEB transcription factors. In C. elegans and human cell culture, hil-1/H1-0 upregulation during low-nutrient states promotes long-term survival and subsequent refeeding-induced recovery. Restoration of C. elegans after prolonged fasting is improved by enhancing the natural downregulation of hil-1 specifically during refeeding. Our study identifies HIL-1/H1.0 as part of an ancestral epigenetic switch during fasting-refeeding that reprograms metabolic and cellular states underlying resilience and restoration.