Prolonged fasting

Prolonged fasting refers to fasting periods of roughly 48 hours up to several days during which only water, electrolytes, and sometimes minimal calories are consumed. After glycogen depletion, the body shifts to fatty acid oxidation and ketogenesis, suppresses IGF-1 and mTOR, and upregulates autophagy. Stem-cell-based regeneration has been demonstrated in rodents; human translation remains limited. Risks include electrolyte disturbances and refeeding syndrome, so prolonged fasting should be medically supervised.