# Prolonged fasting

Prolonged fasting means going without food for roughly 48 hours up to several days. During it, you take only water, electrolytes, and sometimes minimal calories. Once your glycogen runs out, your body switches to burning fatty acids and making ketones. It also suppresses IGF-1 and mTOR, and ramps up autophagy (cellular cleanup). In rodents, this triggers stem-cell-based regeneration, but the translation to humans is still limited. The risks are real: electrolyte disturbances and refeeding syndrome. So prolonged fasting should be medically supervised.

## Sources

- de Cabo R, Mattson MP. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine. https://doi.org/10.1056/NEJMra1905136

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_Canonical: https://longevity-switzerland.com/en/glossary/prolonged-fasting · Part of Longevity Cities · Updated 2026-06-22_