This may be the most important chapter in the whole book, because you absolutely can fast incorrectly and sabotage your results.  If you don’t keep the fast properly, you will not see the type of long-term results that you are looking for (even if you get great short-term results).  Your goal may be to lose weight, but fast weight loss isn’t the only measure of success when you are intermittent fasting.  If your only goal is to lose weight fast, I can give you several recommendations for that.  Of course, you’ll be sorry in the long run.  Reread the Biggest Loser study section and think about whether you want to live your life in a constant state of deprivation.  I sure don’t.  No, our goal isn’t fast weight loss.  Balancing our hormones (insulin, ghrelin, and leptin) so they work the way they are supposed to —that is our goal. Once you do that, weight loss will follow, and eventually it will feel effortless. Take care of your body, and it will take care of you. First of all, remember this—as I explained in a previous chapter, there’s so much more to weight loss than calories in/calories out (CI/CO), and most intermittent fasting plans do not require calorie counting in any way, shape, or form during your eating window or on an up day.  Even so, you want to stick to zero calories during the fast for best results (because if you are eating or ingesting calories in any form, you clearly aren’t fasting).  Even more importantly, you want to keep your insulin from spiking.  That’s the only way you are going to access your stored fat for fuel—and face it—that is why we are fasting to begin with.  Burn, baby, burn! So what causes insulin to spike?  Well, foods do, but we already know that we shouldn’t be eating if we are fasting.  The really sneaky thing that you need to understand is that even zero-calorie beverages and “diet” products can cause your insulin to spike.  You could be ingesting zero calories during your fasting period and STILL be spiking your insulin constantly.  If that happens, you are not going to be able to access your stored fat very well.  Your body won’t burn fat during the fast, and you will miss out on the metabolism-boosting effects of a true fast.  Because your body doesn’t have access to your stored fat for energy, your body is going to perceive that you are in an energy deficit. What does your body do when you are in a prolonged energy deficit?  It SLOWS your metabolism, as we saw in the Biggest Loser study. Just to recap for emphasis:  by spiking insulin during the day, you will not access your stored fat effectively and you risk slowing your metabolism.  When you understand that, you realize that the last thing you would ever want to do is spike insulin by ingesting the wrong thing during the fast. So what DOES cause insulin to spike, other than food or calories?  It’s sweetness.  When we taste something sweet, our bodies “know” that calories are entering the body and insulin is released to deal with the expected rise in blood sugar.  The only problem is that in the modern era, we have figured out how to make things that taste sweet and don’t actually have any calories.  We have created artificial sweeteners and artificial flavors in the lab that have all of the sweetness but none of the calories.  We think we are making a good choice, because we “know” that it’s calories that make us gain weight.  Anything with zero calories seems perfect for the dieter.  Except the opposite is true. You are sabotaging your success and you don’t even know it. If you search for information about various sweeteners and insulin release, you'll find all sorts of contradictory information. Many websites (and studies) seem to suggest that certain sweeteners are safe, and other websites or studies say the opposite.  It can be really hard to know who is right.
Here is a link that might help.  It takes you to the abstract of a study about sweet tastes and insulin release. Insulin release is referred to here as "CPIR", for "cephalic phase insulin release." https://www.ncbi.nlm.nih.gov/m/pubmed/17510492/  This is what they found: "From these results, we conclude that sweetness information conducted by this taste nerve provides essential information for eliciting CPIR."  Pay attention to that.  They found that sweetness caused “CPIR”, which is insulin release.  Even before blood glucose went up, insulin had already been released—from just the sweet taste! Here's something else from the study that is quite interesting. When they cut the nerve from the taste receptors, no insulin was released in response to the sweet flavors. This is HUGE to help us understand the insulin response of sweet tastes.  When the sweet flavors were no longer detectable by the brain, insulin was not released.  This clearly illustrates that the perception of the sweet taste by the brain is essential.  In everyday language:  if you taste sweetness, you release insulin. Here’s another study related to insulin release and sweet tastes: https://www.ncbi.nlm.nih.gov/m/pubmed/18556090/  In this second study, the participants didn’t even ingest the sweetened liquid fully—they merely swished it around in their mouths and spit it out.  From the abstract:  “A significant increase of plasma insulin concentration was apparent after stimulation with sucrose and saccharin. In conclusion, the current data suggest that the sweeteners sucrose and saccharin activate a CPIR even when applied to the oral cavity only.” The subjects in that experiment swished around sweet liquids and then spit them out.  Even though they didn’t ingest anything, their insulin was raised in responses to the sweet taste.  (Note:  some people get nervous at this point and start to worry about brushing their teeth or using mouthwash. Think about it this way.  Yes, you may have a sweet taste in your mouth BRIEFLY from brushing your teeth or using mouthwash, but the duration isn’t going to be for long.  Everyone who knows you has asked me to tell you—please don’t stop brushing your teeth or using mouthwash.  As long as you don’t use it every hour on the hour, you should be fine.  Your family and friends thank you.) So—what's the takeaway from these two studies on sweet tastes and insulin release? When you read somewhere on the internet that aspartame doesn't cause insulin release, or stevia doesn't cause insulin release, or ___________ does not cause insulin release, etc., remember these studies.  A sweet taste=insulin release, even in the absence of calories.  If you are drinking artificially sweetened and/or sweet/fruity flavored beverages during your fast, now you should understand that you are going to constantly spike your insulin levels.  With raised insulin levels, you won’t access your stored fat as readily, and your body may burn muscle mass rather than fat.  Remember—a lot of circulating insulin prevents fat burning.  When you aren’t burning fat for fuel, you will end up with a slowed metabolism rather than a faster metabolism, AND you may end up with less muscle mass.  It may sound like I am repeating myself with this message, and...GOOD! I am.  I keep repeating myself because I want you to understand this very important piece of the puzzle.  In order for you to find lasting success, you have to lower your insulin levels so you can burn fat during the fast. I had a REALLY hard time with this, personally, because I did NOT want to drink my coffee black.  I used vanilla flavored stevia, and it made me happy to have that sweet flavor in my coffee.  I drank a LOT of coffee with stevia during my fasting time, in fact.  I thought it wasn’t affecting me, because I was losing weight.  I also drank sweet fruity teas with names like “baked apple”. Eventually, I struggled with a little bit of weight regain, and told myself that it was normal to regain a
little weight.  I had to work to get about 8 pounds off that I had previously lost.  That’s normal, right? Maintenance is hard. That’s what we have been told, after all. Then, I read Dr. Fung’s book, The Obesity Code, and finally understood what I was risking by spiking my insulin during the fast.  I pitched a fit (that’s what we do here in the South), I whined, and I moaned....and I gave up stevia.  I started drinking my coffee black.  And....I didn’t die.  In a week or two, I was fully used to the taste of black coffee. The better news is that I was able to lose the 8 pounds of weight regain, and I have slowly continued to lose fat here and there with zero effort, ever since.  Eliminating the stevia (and the fruity and sweet tasting teas) made a huge difference in my results, and I am confident that I won’t have trouble with regain in the future.  (In fact, my waist got smaller this year from November 14th – December 14th, which means I lost some fat over Thanksgiving.  How many people lose weight over the holidays?) More importantly, ditching the stevia has made an enormous difference in my level of appetite correction.  It is much easier for me to fast during the day now, and I am more in tune with my satiety signals than ever before.  Lowering insulin levels during my fast by eliminating stevia has made a huge difference for me.  Stevia, you are dead to me. So now we fully understand that we don’t want to spike insulin during the fast.  You may find yourself wondering what you CAN have.  Please refer to the following lists to see what you should and shouldn’t ingest during the fast. Allowed during the fast in any quantity: Water Black coffee (unflavored) Teas (unflavored green tea, black tea, etc., where the only ingredient is some variety of “tea” with no added flavors) Herbal teas (Select ones that are not fruity or sweet.  Especially avoid the fruity and sweet ones that list “natural flavor” in the ingredient list) Sparkling water like La Croix, Perrier, and San Pellegrino (select the unflavored varieties, as the fruit flavors can spike insulin) Probably okay to have small amounts during the fast, but use SPARINGLY: Note:  I avoid everything on this list personally, as I prefer to follow a “better safe than sorry” philosophy.  “When in doubt, leave it out” is a great rule of thumb, and it is what I do.  Some people have had perfectly fine results including these during the fast, and Dr. Fung, my favorite fasting guru, allows these things: Bone Broth (Note:  this should be homemade.  Search online for a recipe.  This is NOT the same thing as bouillons or canned broths, which should be avoided.  You also don’t want to drink this all day long.  Have one cup and move on.) 1 or 2 teaspoons of heavy cream (Note how little this amount is!  Even so, you should not drink cup after cup with heavy cream over the course of your day, as it will add up over time and will keep you from burning your own fat.  Have ONE cup, with 1 or 2 teaspoons MAX, per day.  Personally, I find that heavy cream, even in small amounts, makes me hungry.  My best advice is to learn to like your coffee black.  If I can do it, YOU can do it.) A little coconut oil (This is a tweak that a lot of people in the intermittent fasting community enjoy, but just like with cream, it makes me hungrier.  I also have the philosophy that I would rather be burning the fat from my body than the fat from my coffee cup, so I avoid anything
like this during the fast.) Probably NOT okay to have during the fast:  to be safe, avoid these things: Fruity and sweet flavored teas (even if the label says “0 calories” and no sweeteners are listed.) Flavored coffees (as with the teas—these can taste very sweet.  Do you want to risk spiking your insulin for some “cinnamon roll” flavored coffee?  NO, YOU DO NOT.) Fruit flavored sparkling waters Gum, even sugarless Breath mints, even sugarless For-the-Love-of-God and without question, do NOT have during the fast! Products containing artificial sweeteners, such as aspartame (NutraSweet), saccharine, and sucralose (Splenda) Diet sodas “Diet” ANYTHING Stevia (even though it may be marketed as “natural”) Sugar alcohols (xylitol, erythritol, most things ending with –ol, etc.) Any sweeteners that I forgot to mention (even if they develop a new “miracle” sweetener. Just NO.  Sweet=NO.  No matter what they tell you about it.  No.) Bouillon Canned or store-bought broths Food of any type, even if it is “0 calorie.” (If you have to chew it, you shouldn’t have it during the fast...other than ice.  Chew ice at your own risk, though...your dentist told me to tell you that.) Coffee creamers of any kind (this includes substitute milks such as almond milk, which for some reason, people seem to think should be allowed, but aren’t.) I’m sure there are other things you shouldn’t have that I haven’t thought of.  Here is a great rule of thumb:  If you ever aren’t sure about something, ask yourself this:  does it taste sweet or have calories?  If the answer is yes, don’t try to squeeze it into your fast or rationalize it.  If the answer is “I am not sure,” then treat it as a yes and avoid it. Remember:  I already said that you don’t have to worry about occasional tooth brushing or use of mouthwash.  Yes, those products may contain some sort of sweetener.  Yes, those products may have a sweet taste.  But you are only using them for a moment, so brush, swish, and be done with it. People have a REALLY HARD TIME giving up their favorite things from the lists above.  As I mentioned, I really fought myself on the stevia until I took a hard look at what I was doing to myself. We all know that in any typical diet, there are usually “free foods.”  Pickles.  Diet Jello.  Plain popcorn.  All of these are “low calorie”.  There is even a train of thought in the fasting community that if you are having fewer than 50 calories, you don’t “break the fast.”  Based on my research, I reject that philosophy.  To me, “free foods” smack of “diet thinking”, and my recommendation is to stop trying to work in added items during the fast.  The only things you should have during the fast are the items I specified in the list on a previous page.  There are no “free foods” during the fast.
From experience, let me share this very important piece of advice.  I have been in a lot of diet and weight loss groups over the years, most of which were on Facebook.  It’s a great way to connect with people who have common interests, and these groups can be a fantastic support system.  Do you know what the most common thing I hear from people in these groups about diet sodas/stevia/creamers/flavored coffees?  “It’s okay—they don’t affect MY weight loss.” People are in denial about their beloved sweet, creamy, and flavored products.  Just because they have lost some weight, they assume that everything is working just fine.  And then, these same people never seem to be able to lose the last few pounds to get to goal, or they get to goal briefly and then have rebound weight gain.  (In fact, rebound weight gain is the biggest problem that I see from these people.)  The heavy diet soda/flavored coffee/sweetener users NEVER have results as good as the people who avoid the artificial sweeteners during the fast.  They also struggle more with hunger and compliance, because their satiety signals don’t get into balance as easily.  These people are stuck in the CI/CO mindset, where it is only about the calories.  When you understand how insulin works to lock away your fat stores, you completely understand why it’s counterproductive to include products that will spike your insulin during the fast. Remember this:  if you try to get away with having the forbidden items, you are only cheating yourself.  You may think you are losing weight just fine, but you aren’t really accessing your fat as effectively as you could be, because of the constant release of insulin.  Instead of reaping the beneficial hormonal effects of the fast, you are actually causing hormonal damage—you just can’t see it