CHAPTER 7
How to Practice Intermittent Fasting When someone first starts fasting, they usually have a few questions: “Exactly how many hours it will take to get into ketosis?” “What level of ketosis should I aim for?” “How long do I have to fast for maximum fat burning?” These are all reasonable questions, but difficult to answer in a general sense. Many things influence the rate of ketone production; for instance, the amount of liver glycogen you had going into your fast (which is affected by how much carbohydrate you ate prior to fasting). If you typically eat a low-carb or ketogenic diet, then you won’t lay down much glycogen at all and you’ll enter a ketogenic state more quickly. The amount of exercise you do while you’re fasting has an impact as well. This is pretty obvious, though—the more energy you use in the fasted state, the more fat and ketones will be used because those are your main energy sources during a fast. Your size and body composition matters, too, as well as how fit your muscles are and how good they are at using fats, glucose, and ketones. So the focus on level of ketosis and exact timing to optimize ketone production is a bit misplaced. What’s essential is that you keep up a fasting practice and have a varied exercise practice. Do that, and you will get better at producing and using ketones, and better at using fat directly, too. This is what you want. It’s also hard to tell exactly at what time of day your ketones levels will be highest. If you’re looking for some marker to decide how long to fast, pay attention to how you feel. Fasting and ketosis increase your sense of well-being. They make you feel good. The caveat is you have to get through the transition from eating all the time and operating solely on a glucose-based metabolism, to eating less often and training your cells to use fat again. That’s why I recommend a minimum six-week commitment to any fasting plan you start. For the rest of this chapter, I’m going to outline some of the popular intermittent fasting patterns out there, simply because I think it helps to have some models when you’re starting out. This chapter will also include interviews with people who incorporate intermittent fasting into their own lives, so you can see first-hand accounts of how it works. Remember, don’t get too caught up in the precise timing or structure of these patterns. The important thing is to begin a fasting practice that is feasible for you and make it a consistent part of your life. There is no perfect schedule except the one that works for you.
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