The Food window
The Food Window versus Elimination Diet.
There are three ways to transition to a new eating program: changing your food, changing your eating habits, or changing both. Most people will likely prefer to start with one or the other because doing both at once can be overwhelming. Which is better? I believe the easier route is to use the food window or fast because you can keep eating familiar foods while your body develops metabolic flexibility. Metabolic flexibility means you can burn sugar (glucose) and/or ketones as fuel. Once you can fast for 15+ hours at a time, your body will produce and use ketones. At this point, it becomes easier to change your diet and adjust your taste buds. There’s nothing wrong with taking a different approach, or even combining the two methods, if you think you can. This isn’t a race or a competition. Do what feels best to give yourself the best chance at success. A year from now, when you’re on a completely different eating plan, it won’t matter how you got there. If you prefer to start by changing your diet, look for Dr. Ede’s book, Change Your Diet, Change Your Mind, in the Library. She details a food-first approach.
The Food Window
One way to think about fasting is to consider how long we eat, or our “food window.” Dr. Gundry and others refer to this as “time-restricted eating.” Regardless of what it’s called, using a food window or time restriction allows the digestive system to rest and repair, enables the body to reset its hormones, and activates the alternate fat-burning pathway. This is the first step to achieving optimal health. It’s not as hard as it sounds, but there is an adjustment period during the transition, and some people will find it easier than others. Be kind to yourself. Remember, this is a destination, not a race. Click the buttons below to start healing and improving your life in ways you can’t imagine!
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We know that our ancestors were hunter-gatherers for hundreds of thousands of years—perhaps even a million years or more. They woke up and searched for food. They hunted animals, dug up tubers, and gathered nuts and berries. They probably ate almost anything they could find. There were no grocery stores or refrigerators. Starvation was a primary concern. Our ancestors were fortunate to find one meal a day and often went days without food. We evolved to be a hybrid that uses food when it is available and body fat stores when food is unavailable. This conversion from using glucose to using fat is often called metabolic flexibility and is critical to our health. A lack of metabolic flexibility is the main cause of illness. When food is scarce, our bodies switch to using ketones, a more efficient fuel source than glucose.
Today, we have access to a wide variety of foods. We can eat at any time of day. With so many choices, we don’t know what to do. We have stopped eating the way our bodies evolved. Eating all day long keeps glucose levels high, pushing insulin levels higher until insulin resistance develops. Welcome to “pre-diabetes.” If this continues, our tissues will stop responding to large amounts of insulin. The pancreas cannot produce more insulin, and glucose levels become uncontrolled. Now, we have diabetes. Chronically high insulin levels also disrupt other hormones, such as cortisol. This leads to high blood pressure, elevated triglycerides, anxiety, and poor sleep. These issues continue the path to worsened health. This chronic imbalance is inflammatory and can lead to damage in many organ systems. When three or more systems are affected, the condition is labeled “metabolic syndrome.” Examples include high blood pressure, high triglyceride levels, and diabetes. People often say, “Diabetes runs in my family,” because families typically respond similarly to this imbalance. Another way to think about this is that the way your family responds to high insulin levels runs in your family. Other families may respond with heart disease, an inflammatory response unrelated to cholesterol, or brain disease, such as dementia. What about glaucoma? I think it is also a metabolic response that runs in families. Almost all of our common “diseases” are the result of inflammation caused by our food. As Dr. Robert Lustig writes in his book Metabolical, “The holy grail of modern medicine is that you can’t fix healthcare until you fix health, and you can’t fix health until you fix food.” It all comes down to food.
Chronic feeding prevents the body from switching to fat burning, forcing you to rely solely on glucose for fuel. How can you tell if your body can’t switch over? Do you ever get “hangry”? If your body cannot switch to fat burning, it will crash as glucose levels drop, causing severe agitation, anxiety, and often outright anger. “I must eat NOW!” your body screams. This is a classic symptom of glucose-only metabolism and proof that you are eating too often throughout the day.
It doesn’t have to be this way. Almost all illnesses and the “hangry” state are reversible through fasting. Even those with irreversible damage due to damaged organs can experience improvement. Shorter eating windows allow the digestive system to rest and enable everything to return to normal. Yes, everything: body weight, hormones, blood pressure, and mental state. Everything. Fasting is a natural part of human health and the key to reversing insulin resistance and promoting healing.
Fructose - the Anti-Fast
I need to talk about sugar one more time. The less sugar and sweets you consume, the easier and faster it will be to fast. Sugar tells your body not to burn fat. Fructose, which is found in fruit and in large amounts in table sugar and high-fructose corn syrup (HFCS), directly causes weight gain by turning off the brain function that tells us we’re full. This makes us eat more because we think we’re still hungry. It’s like a broken thermostat on a furnace that reads the wrong temperature of the house. Fructose also increases triglycerides, blood pressure, and insulin resistance, which can lead to prediabetes and diabetes. These are the opposite effects of fasting. Fructose is the anti-fast. Eating sugar while fasting is like pressing the brake and gas pedals at the same time—even more so when sugar is combined with alcohol.
The Different Types of Fasting
The human body is designed to survive and adapt to its environment. You can control the type of response by adjusting the duration of the fast. It’s a good idea to mix up the types of fasts you do. Doing the same thing all the time will reduce your results. Below are examples of different types of fasts to choose from based on your goals:
The basic fast for intermittent and daily: 12 -16 hours
This is where you should start. The basic fast allows your blood glucose to drop, which triggers the switch to fat burning and ketone production. For most people, it takes 14 to 15 hours of fasting for insulin levels to return to baseline and for full ketosis to begin. Depending on how often you eat and how dependent your body has become on sugar, this zone may or may not be difficult for you. Do not attempt to bypass this stage and proceed to longer fasts. Your body cannot make this switch rapidly. It may take a couple of weeks for the change to happen. You will know you have begun to switch to ketones when you no longer feel an overwhelming urge to eat when you wake up in the morning.
Here’s a special tip: Do aerobic exercise in the morning on an empty stomach. This strategy is not often discussed, but it’s a fantastic way to supercharge your transition to fat burning. Wake up and move! Doing any aerobic exercise in a fasted state triggers your body to burn fat. Perhaps this is due to our hunter-gatherer genetics, when our ancestors had to hunt before eating. Take it easy on your workout until your body makes the switch, and then you’ll be impressed by your unlimited energy and even better athletic results!
Ketosis/ Autophagy fast 15-18 hours
Okay, you’re a pro now! At this level of fasting, we achieve full ketosis, mental clarity, and unlimited energy. After 17-18 hours, autophagy begins, which is the process of internal cellular cleanup. Your insulin level is at baseline and your blood glucose level is maintained purely by burning fat. You are a fat-burning machine! Congratulations! You will notice that you no longer feel hungry, and eating becomes optional. This is the gateway to the longer fasts detailed below. This level of fasting is also associated with decreased anxiety as cortisol levels normalize. Men, prepare to update your wardrobe after three to four weeks of this type of fasting.
The 24 hour fast- Gut Healing repair and full autophagy
Once you reach the 18-hour mark, it’s easy to extend to 24 hours. This is a great option every month or so. After 24 hours, your gut has completely rested and is in full repair mode. Ketones run the show and insulin is at baseline, allowing for total receptor recovery. Some people like to use a 24-hour fast as a type of recovery from a “cheat” day. I often fast for 24 hours when traveling because there isn’t anything worth eating at airports anyway, and it’s convenient not to eat.
The 36-48 hour metabolic fast
Hitting 36+ hours every few months is a good way to bust through plateaus. However, if you get into a routine, your body will adapt and become more efficient at it. However, we don’t want efficiency; we want the body to stay flexible. Metabolic flexibility is achieved by changing the routine. This is similar to bodybuilders’ strategy of changing exercises for greater gains.
Stem cell and Immunity boost 48-72 and beyond
Only consider these lengths once or twice a year. After 48 hours, the dopamine system resets, which greatly helps those with anxiety and depression. All the benefits of shorter fasts are included here, too. As you approach and surpass 72 hours, an incredible stem cell regeneration process begins. There is ongoing research and some good evidence that a 48–72-hour fast has the ability to fight cancer. Cancer cells use only glucose and cannot metabolize ketones; therefore, any amount of ketosis from a longer fast is potentially beneficial for cancer recovery. Definitely discuss fasting with your doctor.