Beginners Guide to Extended Fasting

So you’ve tried many different dietary interventions but none of them seem to provide you with the sustained benefits that you require. As a result you’ve decided to try extended fasting.

Fasting for over 2 days has many challenges. First of which is the social disapproval. Friends and family are very quick to judge something that they don’t understand. How can you blame them? Food companies have changed the societal narrative from one that used to embrace fasting to one that encouraged constant feeding. A great article on the history of fasting can be found here. [1]

Secondly, the cravings are about more than just satiety. Being surrounded by food makes it hard not to gravitate towards a snack when we’re bored or depressed. [2]

Thirdly, energy is an issue when you first start. I will go over how to prepare your body in order to overcome this.

The fourth issue is that the digestive system and the gut microbiome change when food isn’t around. [3] Slowly transitioning back to eating is important to avoid any gastrointestinal discomfort or permanent damage.

So why fast for so long?

Daily intermittent fasting has its benefits but the real magic starts to happen at the 48 hour mark. Blood sugar regulation (which trickles down to improved blood cholesterol and triglycerides), restoring gut health, fat loss and autophagy/mitophagy (the “self-eating” of damaged cells/mitochondria) are just a few great reasons why extended fasting can change everything for you.

Preparing for the Fast

Fasting causes a shift in the body’s energy partitioning. The typical 21st century diet is carbohydrate based. These carbohydrates are broken down into glucose or fructose upon digestion. The glucose is used to fuel your cells.

In my opinion, our excess availability of carbohydrates has caused the majority of society to develop a physiological adaptation to using glucose. Glucose is relied on so heavily for fuel that the utilization of stored fat or ketones is not within the realm of our body’s understanding anymore. I think that’s the reason why most people feel so lethargic upon giving up food for a few hours. They have an abundance of fat stored which the body does not know how to utilize.

That is what fasting can fix.

In my experience with longer fasts (5 day fast and 6 day fast) it is very beneficial to induce ketosis through a ketogenic diet before starting. This will allow you to adapt to using stored fat (in the form of ketones) and avoiding a lot of the lethargic effects of fasting for the first time.

If you are already eating a low carb, high fat ketogenic diet you can ignore this.

Here is what I suggest. Let’s assume that you currently eat 3 meals a day (all of which contain carbohydrates and protein).

Week 1 – Remove the carbohydrate component from one of your meals and replace it with a good source of fat such as avocado, olive oil, almonds, butter, eggs, etc.

Week 2 – Remove the carbohydrate from a second meal and replace it with a good source of fat.

Week 3 – Remove all other sources of carbohydrates from your diet so that you are left with proteins and fats.

Important to note that you do not want to be starving in any of the phases above. If you’re hungry, eat more fats to stay full. Counting calories is not required here. You will naturally limit your calories as a result of the satiating effects of the diet.

Once you reach week 3 you would want to sustain that way of eating for at least 2 weeks (ideally 4 weeks). If you haven’t done this before, it is normal to reach a point within this period where you start feeling brain fog, lethargy and dizziness. That is normal.

This period is called the carb flu. It is the withdrawal symptoms of giving up carbohydrates and sugar. There are studies that demonstrate sugar addiction and how real it really is! [4] It is a sign that your body is learning to shift energy sources. In this period it becomes very important to stay hydrated. If you feel tired drink 500 mL of water. Aim for at least 2 L of water each day.

Electrolytes are also essential at this point. The big 3 are sodium, magnesium and potassium. Consuming a serving of leafy green vegetables in all of your meals and using salt (preferably pink himalayan salt) will ensure success.

With all of this in mind, it is important to plan this fasting period (and all of the preparation) at a time when you don’t have any social obligations to fulfill.

Starting the Fast

So you’ve experienced a couple weeks of ketosis, and you’re ready to get started. This is probably the easiest part of the intervention. One rule: DON’T EAT

I’m kidding. That’s the main rule but there are some other important rules to follow to ensure that you maintain high energy and productivity through the fast. The fasting days are by no means “a write off”. You should be at the top of your game assuming you do everything right.

Now that you’re not eating, hydration and electrolytes become even more important. Drinking water is the easy part. Finding out how to take in electrolytes is the hard part. Since you’re not eating, vegetables are no longer an option for a suitable amount of micronutrients.

My personal preference is to use pink himalayan salt whenever I feel lethargic. It always seems to do the trick. Just place some on your palm and lick it all off. Other options could be to drink a salted cup of bone broth or take magnesium supplements.

I prefer to stay away from supplements since they can cause some gastrointestinal discomfort (when consumed without food) and the bone broth trick should be used only if it’s absolutely required.  Bone broth is a strong source of collagen protein. Collagen protein is the main protein that holds the muscular tissue of organs together. However, three of the four amino acids (proteins) that make up collagen are glucogenic. This means that they can elicit an insulin response which will slow your progress during a fast. This trick is great when you’re starting out but should be phased out the more you become experienced.

Approved Drinks

There is typically a lot of confusion surrounding the drinks that are allowed. Fasting is about more than just sustaining a calorie free period of time. It is more importantly about not consuming anything that can stimulate an insulin response in your blood.

The drinks that can be consumed are: black coffee, tea (no sweetener), water, etc.

Why Sweeteners Don’t Fit

Sweeteners are often the replacements that are sought out to fill the void left by sugar. Unfortunately, sweeteners have a unique response. Although they do not elevate your blood sugar, they can stimulate an insulin response. This is a piece of information that I picked up from listening to Dr. Adam Nally speak about his clinical application of ketogenic diets. I also feel the effects of these sweeteners on a low carb diet. I CRASH HARD.

It is also important to note that when you buy a sweetener like stevia, it is usually bound to maltodextrin. Maltodextrin has an effect on blood sugar, though. It eliminates the intended purpose for buying stevia. As mentioned above however, stevia itself can also have an insulin response independent of blood sugar.

Although this response might not apply to everyone, it applies to the majority and should be avoided if you can help it. There is good news though! There is only one sweetener that does not seem to have this effect and that is aspartame.

So here is a list of sweeteners to avoid:

  • Erythritol
  • Maltitol
  • Mannitol
  • Sucralose
  • Stevia
  • Xylitol
  • Sorbitol
  • Ace K (Acesulfame potassium)

It would help to test these for yourself and see how you feel. It would help to quantify what happens through blood sugar or blood ketone measurements throughout your fast.

Ending the Fast

When you’ve decided to end your fast, DO NOT start eating everything in sight. It is important to gradually reintroduce your digestive system to food. Besides, you won’t actually even be that hungry. This is hard to believe but quite amazing when experienced after day 2.

Fermentable foods like sauerkraut that are rich in probiotics should be used in order to make sure that a healthy colony is re introduced. Prebiotics coming from leafy green vegetables are also very important.

My ideal first meal is usually steamed green vegetables, half a cup of sauerkraut and olive oil. It goes down easily and keeps me full for a while. A few hours later I start eating protein again, preferably from eggs to start with.

In my first fasting experience, I found it to be a very good opportunity to take a strong probiotic supplement. My probiotic of choice was the medical grade VSL #3. This was a great decision because it seemingly removed all signs of anxiety that I was experiencing prior to starting the fast. Science is just starting to show the link between depression, anxiety and imbalanced gut bacteria. [5]

Probiotic supplements are optional but do help to ensure that you return to a normal digestive state. Probiotics from supplements or food can be a great way to eliminate or reduce a long list of autoimmune diseases (such as leaky gut syndrome) that could be bothering you. [6]


Fasting is a skill and like any other skill requires consistent practice. With time, your abilities will increase. Step one is to shift your perspective to one that is confident in your ability to accomplish this new personal feat.

It is so empowering to know that you do not require food to operate but instead that you operate better without it. All of the blood that would normally supply your digestive system is rerouted to your brain. To add to that, you’re fueling with energy dense ketones instead of glucose! You reach a level that you forgot you had or didn’t even realize you had.

If your body tells you that it’s time to end a fast, then listen to it. If you’re sick or travelling, end the fast. You aren’t obligated to complete a set amount of time, just start  building that skill and work it in around your schedule.


[1] Intensive Dietary Management. “Fasting – A History Part I”. [Online]. Available:

[2] Psychology Today. “Do You Eat Out Of Boredom?”. [Online]. Available:

[3] All About Fasting…For Health And Healing. “Guidlines for Breaking a Fast”. [Online]. Available:

[4] NCBI. “Evidence for sugar addiction: Behavioral and neurochemical effects of intermittent, excessive sugar intake”. [Online]. Available:

[5] Neuroscience Research. “Gut–brain axis: how the microbiome influences anxiety and depression”. [Onine]. Available:

[6] Healthline. “How Balancing Gut Bacteria Can Ease Autoimmune Diseases”. [Online]. Available:

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