UNDERSTANDING INTERMITTENT FASTING

The concept of intermittent fasting (IF) is not particularly new, but over the last several years it has garnered a lot of attention and new research. It is what it sounds like — periods of fasting alternating with periods of non-fasting. While the vast majority of research has been conducted in animals, there have been more human-based studies the last couple of years that have analyzed the biological and physiologic changes that occur once a person participates in an IF program.

There are two major types of IF eating schedules. The first is the 5:2 schedule, where for five days a person eats how they typically would, then for two days of the week calories are restricted to 800 or less. The one caveat is that the fasting days should not be consecutive.

The second type of eating schedule, which you will follow on Clean & Lean, is time restricted feeding (TRF). On it, food is consumed only during certain hours and there are two periods of fasting. The duration of the feeding periods can vary. Most commonly, they are 8, 10, or 12 hours in length. For example, a 16:8 strategy includes 16 hours of fasting and 8 hours of feeding; the 14:10 strategy would be 14 hours of fasting and 10 hours of feeding.

The two IF eating schedules would look something like this:

5:2 INTERMITTENT FASTING

Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Normal Normal Fasting Normal Normal Fasting Normal
eating eating (800 eating eating (800 eating
calories calories
or less) or less)

TIME RESTRICTED FEEDING (TRF)

7 A.M. 7-10 A.M. 10 A.M.-8 P.M. 8 P.M.-10 A.M.
Wake up Fasting Feeding Fasting

Benefits of IF

Researchers acknowledge that while IF has been used for several years, and there have been studies performed to analyze the pros and cons of this eating strategy, much more work needs to be done to make validated, scientifically based claims. There have been, however, lots of anecdotal evidence about the effects of IF as well as animal studies and early human trials. While these observations are not always definitive and conclusive, they give us a clearer window through which we can inspect the potential benefits of this eating strategy. The evidence suggests that IF can help in weight loss, better regulate blood sugar levels, increase blood levels of human growth hormone, and induce cellular repair processes.

Given the various research studies looking at IF, there are many theories that have been suggested as to why there might be appreciable physiological benefits. Mark Mattson, a senior investigator from the National Institute of Aging, has studied the hypothesis that during the fasting period cells are actually subjected to a mild stress. Mattson and others believe that cells react by making adaptations that increase their ability to handle this stress and possibly resist disease. It's akin to the adage, "Whatever doesn't kill you, makes you stronger." In other words, fasting deprives cells of nourishment, which is stressful. But the cells change and adapt to handle tough conditions. Scientists believe that these changes make the cells tougher and better at preventing or fighting disease.

Intermittent fasting does not mean that you can simply eat whatever you want or how much you want during feeding times and still lose weight. One of the big misconceptions held by many people is that as long as they don't violate their eating time parameters they can indulge in as many sweets, alcoholic beverages, or fried foods as they desire. Not only is this untrue, but it can potentially be very harmful to one's health and efforts at losing or maintaining a healthy weight.

Calorie consumption still matters even while employing the IF strategy. For example, whether you consume 3,700 calories within a regulated 10-hour time span or throughout the day as is typical, the basic equation of weight loss still holds. Calories in must be less than calories out in order to lose weight. The vast majority of people who are consuming 3,700 calories are not going to lose weight regardless of the number of hours it takes to consume those calories. The body must do something with the caloric energy that is consumed. If you don't burn off the calories, the body will store them in the form of fat, which will not only increase your weight but prevent you from attaining that leaner physique you're trying to achieve.

Feeding Times

There are three TRF schedules that we will focus on in this book: 16 hours of fasting with 8 hours of feeding (16:8), 14 hours of fasting with 10 hours of feeding (14:10), and 12 hours of fasting with 12 hours of feeding (12:12). If you're not sure which schedule will best fit you, try the 14:10 plan first. If it seems too difficult after a few days, then switch to the 12:12 plan. If it seems too easy, and you are up to the challenge, give the 16:8 a try. While the specific hours you choose to start and end your periods of fasting and feeding can change according to your preference, on the next page are samples of what a schedule might look like. You choose the feeding timetable that works best for you, but keep in mind that the smaller feeding window might produce better results.

THE CLEAN & LEAN RULES

I have designed Clean & Lean to be as accessible and versatile as possible. I don't expect you to go to a grocery store and empty your bank account in order to find the items on the list. I don't expect you to be locked into your house for the next thirty days so that you are in complete control of your food environment and all the ingredients that go into your food. You will be at work or at a restaurant or in an airport, and you still need to eat and not feel like you're a criminal because you might have to slightly alter the plan. Remember, the purpose of Clean & Lean is to reintroduce your body to the wonders of clean eating and to give your organs a break from all the processed foods that dominate the choices in our stores and restaurants.

Clean food and clean recipes don't have to be boring or flavorless, despite the image conjured of plain chicken and bland raw vegetables. In fact, clean foods can be just as tasty and exciting as those processed foods that are loaded with lots of additives and artificial flavor enhancers. Spices and clean condiments can go a long way to liven up recipes and thrill your palate. We have grown so accustomed to processed foods that we need to be reacquainted with the authentic flavors of real, natural food. So take your time with the ingredients. Taste them raw or with spices — something that will happen over the next thirty...