In a modern world where it's considered normal to consume 3 meals and additional snacks everyday (otherwise you will get sick), fasting can be considered an outrageous and even dangerous practice. One of the biggest fears of fasting is the fear hunger, the false hunger that most people are afraid of while depleting their glycogen stores (the body sugar storage). Fasting has often been associated with religious customs. It is time to define a line between the two. In Periodic Fasting, I embark on a timeless journey from the very beginning of life on Earth, through early human societies, through the middle Ages and into modern days to explore the concepts and practices of prolonged fasting and intermittent fasting (IF). Periodic Fasting is about: 1. My early life encounters with fasting in the small village of my grandparents (using a high-carb diet). 2. How primitive life-forms on Earth and fasting co-evolved; fasting in the animal kingdom. 3. Early hominid species, food restriction, and meal frequency. The first organized human societies and the switch between irregular feeding to regular dietary patterns. Circadian rhythmicity and meal timing. 4. The personal story of a man from the middle Ages who started consuming less food in his mid-thirties because of poor health and lived to 102 years (narrated by himself). 5. The dozens of prolonged fasting experiments in the beginning of the 20th century; fasting as a cure to many ailments. 6. How people can live without food for 139, 236 and even 382 days (medically supervised experiments). Details of 7-40 days fasts done by lean people for rejuvenation, detoxification and increased life span. 7. The emerging science and the studies of fasting from the mid-20th century (pathological implications - diabetes, obesity, CVD, cancer, and others). 8. How fasting and semi-starvation can be totally opposite: disturbing stories from the Second World War. 9. The molecular mechanisms of fasting: what happens when your body focuses on cell repair and tissue rejuvenation, instead of digesting food. 10. How the secretion of some hormones may be widely misunderstood: especially thyroid hormones and insulin. On muscle-loss phobia, mainstream media, and bro-science. 11. The modern-day science of prolonged fasting and intermittent fasting (AMPk, SIRT, FOXO, etc). 12. My personal prolonged water-only fasting experiment; insights into refeeding and realimentation after long-term fasting. 13. My 1 year and 3 months daily intermittent fasting protocol (still on-going). My ever-adapting exercising protocol (lifting), what I eat everyday, what supplements I use and what other cool strategies help me stay consistent and compliant with the protocol. 14. How I combine intermittent fasting (IF), a well formulated ketogenic diet, and calorie restriction to immensely increase the quality of my life, and paradoxically, never feel hungry; how energy levels and mood can increase if you correctly adopt a fasting protocol. Once armed with this knowledge, you will drastically alter your perspective about your body's limits.