Intermittent Fasting For Dummies. Janet Bond Brill
the timeline of events
What is the physiology of fasting? Although everybody responds to fasting a little differently (genetics, health, and age all play a role), there is a general timeline of events — a predictable set of metabolic responses as your fast stretches from hours into a day or longer. (For a much more detailed discussion of the different metabolic states your body goes through when practicing intermittent fasting, refer to Chapter 5.)
1 You have no food coming in, so you exhaust your supplies.Your body has tapped into your liver reserves of blood sugar to continue to keep your blood sugar level in the normal range. You’re now in what’s termed a catabolic or breakdown state.
2 You enter the fasted state; your liver has run out of its sugar reserves.This triggers the liver to manufacture new sugar from noncarbohydrate sources (scientifically termed gluconeogenesis) to continue to supply energy to the cells. With no carbohydrates consumed, the body creates its own sugar by using mainly fat. This marks the body’s transition into the fasting mode. Studies have shown that gluconeogenesis increases the number of calories the body burns, meaning when your metabolism starts to increase.
3 You flip your metabolic switch.One key mechanism responsible for many of the beneficial health effects of short-term, intermittent fasting is flipping of the metabolic switch. The metabolic switch is the body’s preferential shift from utilization of blood sugar to fat and fat-derived ketones for energy. In this step, your body breaks down fat, shuttling it to the liver, which creates ketones from fat to use for energy. The metabolic switch typically occurs between 12 to 36 hours after cessation of eating.
4 Extended fasts (longer than 36 hours) begin to slow metabolism down.That’s why you shouldn’t practice extended fasting with intermittent plans. After about 36 hours, the body stops using these energy sources (sugar and fat). The fasting mode then transitions to the more serious starvation mode.
5 You enter starvation mode.At this point, your metabolism has slowed dramatically, and your body begins to burn your own muscle protein for energy. The lack of essential nutrient intake plus using muscle for energy sets off an alarming cascade of dangerous complications.
Considering Your Intermittent Fasting Options
The most effective dietary plan is the one you can adhere to for the long term while still living your best life. If you want to lose weight and are sick and tired of counting calories, then this eating pattern may be the right fit for you. The popularity of intermittent fasting lies in its simplicity and the fact that the fasting periods are time-limited, which people find easier to maintain than traditional diets.
Intermittent fasting is not only for people who want to lose weight, but it’s also a phenomenal lifestyle plan for individuals who want to improve their health, fight aging, and simplify their lifestyle. The scientific data shows intermittent fasting has powerful effects on your body and brain and may even extend your life. Chapter 6 discusses the miraculous health benefits linked to intermittent fasting.
Part 3 discusses the five most common ways of practicing intermittent fasting in detail. These different alternative protocols are as follows:
Time-restricted intermittent fasting: The time-restricted intermittent fasting, also called the eating window plan, is by far the most popular plan, because many rave about it being the easiest to follow. This plan consists of fasting for a daily 16-, 18-, or 20-hour consecutive period and setting your daily eating window for the remaining 8, 6, or 4 hours (albeit, you can use other time windows). Check out Chapter 9 for more details.
Warrior intermittent fasting plan: The warrior intermittent fasting plan is based on the eating patterns of ancient warriors who ate very little during the day and then feasted at night. Flip to Chapter 10 for the details on this method of intermittent fasting.
Alternate day intermittent fasting: Alternate day fasting (ADF), another form of intermittent fasting, involves fasting one day, eating the next, and repeating. Chapter 11 gives you the lowdown on this method.
5:2 intermittent fasting plan: The 5:2 plan, also known as the fast diet, entails eating 500 to 600 calories on two nonconsecutive days of the week. Chapter 12 explains the ins and outs of this plan.
Eat-stop-eat intermittent fasting: This plan requires fasting for a full 24 hours, once or twice a week. Head to Chapter 13 for how to incorporate eat-stop-eat intermittent fasting into your life.
MAKING THE EVOLUTION CONNECTION WITH TODAY’S INTERMITTENT FASTING
For more than a hundred thousand years, humans roamed the earth. They were foragers, so they’d fast until they found, caught, or killed their food. Like so many animals in the wild, human’s paleolithic ancestors regularly experienced extended time periods with little or no food. The timing of eating depended on the availability of food; they ate opportunistically. Because humans evolved in environments where food was relatively scarce, they developed numerous adaptations that enabled them to function at a high level, both physically and cognitively, when in a food-deprived/fasted state. Importantly, metabolic, endocrine, and nervous systems evolved in ways that facilitated high levels of physical and mental performance when in the fasted state (from approximately 12 to 36 hours without food). Both the metabolic shift to ketone utilization (a chemical derivative of fat), and adaptive responses of the brain and nervous system to food deprivation play major roles in the fitness-promoting and disease-allaying effects of intermittent fasting.
Hunter-gatherers gathered berries off bushes; dug up tubers; hunted mammals; scavenged meat, fat, and organs from previously killed carcasses; and discovered how to fish and hunt with spears, nets, bows, and arrows. Furthermore, their activity level is a far cry from the sedentary lifestyle so many people today lead. By