FASTING PROTOCOLS
19:5 Intermittent Fasting: Maximum Autophagy in a 5-Hour Eating Window
Medically Reviewed & Fact-Checked by FastingTracker Medical Board • Written by
Aly Owen •
Updated: Sep 21, 2026
✨ Key Takeaways
- Learn the best practices of intermittent fasting for optimal health.
- Understand how to track your fasting windows effectively.
- Discover the science-backed metabolic benefits of fasting.
19:5
Fast: 19h | Eat: 5h
Eating window: 2:00 PM–7:00 PM
19:5 IF gives only 5 hours to eat. At 19 hours of fasting, SIRT1 (the longevity enzyme) is maximally activated and the body runs entirely on fat.
🔬 Expert Note: 19:5 is strictly for experienced fasters (3+ months of 16:8 or 18:6). Not recommended for women with hormonal sensitivity or those with high physical demands.
📚 Scientific Studies & Medical References (5 Sources) ▼
FastingTracker adheres to strict editorial standards, citing peer-reviewed clinical trials and authoritative medical institutions.
- New England Journal of Medicine (2019): de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 381(26):2541-2551. PubMed 31881139 • DOI
- Cell Metabolism (2014): Levine ME, Suarez JA, Brandhorst S, et al. Low Protein Intake and Periodic Fasting Promote Longevity and Autophagy. Cell Metab. 19(3):407-417. PubMed 24606898 • DOI
- Obesity (Silver Spring, 2018): Anton SD, Moehl K, Donahoo WT, et al. Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting. Obesity. 26(2):254-268. PubMed 29086496 • DOI
- Annual Review of Nutrition (2017): Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 37:371-393. PubMed 28715993 • DOI
- Autophagy (2010): Alirezaei M, Kemball CC, Flynn CT, et al. Short-term fasting induces profound neuronal and systemic autophagy. Autophagy. 6(6):702-710. PubMed 20534972 • DOI
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