Intermittent fasting (IF) is an eating schedule which alternates between fasting and feeding. You set a time window for eating, eat only within that window and fast the rest of the time. For example, you may eat only between the hours of 10:00 AM and 6:00 PM.IF is not a diet in the conventional sense, but rather, a pattern of eating. Certain types of intermittent fasting can be incorporated daily, while others are meant only for longer blocks of 3 to 5 days.Each style carries its own benefits for metabolism, disease prevention, cellular repair and psychological well-being. In this guide, we'll go through all of the benefits, ways to do intermittent fasting and frequently asked questions.Intermittent fasting recently gained popularity in the ketogenic, weight loss and bodybuilding communities, but it's not new. It has been used therapeutically since the 1900s to treat obesity, epilepsy and diabetes.Intermittent fasting has historically been a normal part of life for humans and many organisms. It's a way of tapping into the ancient knowledge that already exists within your biology. Scientists and celebrities alike are popularizing this way of eating.IF is healthy, with benefits from better brain function to protein sparing weight-loss and cancer prevention, and best of all it's easy.History of Intermittent FastingCompared to traditional "dieting," fasting is simple and unambiguous. It's always been done. You already unconsciously do IF whenever you skip breakfast or dinner. Historically, during hunter-gatherer days, our ancestors were in a fasting state while seeking food.When agriculture was established, civilization came next. But when food was scarce or seasons changed, fasting was still a way of life. Cities and castles stored grain and cured meat for the winter. Before irrigation, lack of rain meant famine, and people fasted to make their stored food last as long as possible until the rains came back and it was possible for crops to survive again.Religions flourished in this arrangement of people living closer together, sharing and spreading belief and traditions. And religions also prescribed fasting. Hinduism calls fasting "Vaasa" and observes it during special days or festivals, as a personal penance, or to honor their personal gods. Islam and Judaism have Ramadan and Yom Kippur, when it's forbidden to work, eat, drink, wash, wear leather and have intercourse. In Catholicism, it's six weeks of fasting before Easter or before Holy Week.The Science of Intermittent FastingThe modern era of agriculture and factory-laden "food" (or food-like substances) has completely changed the way humans view and consume food on a daily basis, leading to the laundry list of health problems that our society faces today.Although IF is an ancient practice, the science behind its many health benefits is just recently being exposed to mainstream society. When you fast, you basically allow your body to naturally cleanse, repair and regenerate itself for optimal function.Three of the main health-promoting mechanisms associated with fasting include the metabolic regulation of circadian biology, the gut microbiome and different lifestyle behaviors.