A plate with an alarm clock on it

A common thread in many of my articles is the synergistic relationship between intermittent fasting and the ketogenic diet. Contrary to popular belief, intermittent fasting and keto are not new health strategies, they actually share a long history together.

In an earlier post I outlined the origin of the ketogenic diet with respect to its application in the treatment of epilepsy, and how it all started with fasting. A quick recap of the connection goes as follows:

  • Researchers in the early 1900’s discovered that fasting significantly reduced the frequency and severity of seizures in patients with epilepsy.
  • In 1921 endocrinologist Rollin Woodyatt made the connection that ketone bodies, or ketones for short, produced in the liver during starvation were involved in reducing epileptic seizures.
  • Dr. Woodyatt is also commonly credited for identifying the fact that a diet rich in fats and low in carbohydrates is more effective at producing ketones than fasting alone, and he designed the initial ketogenic diet protocol.

In the same article I also highlighted the fact that fasting and keto go back even further and how they, along with paleo, collectively emulate the original human diet we have evolved with for millions of years. Research has confirmed that early humans consumed more than 10 times the amount of fat we do today, did not have access to high carbohydrate sugary foods, and often went without food for extended periods of time.

Research has also confirmed that early humans were much healthier than we are today, and they did not suffer from many of the ailments that we currently contend with.

The Benefits of Intermittent Fasting
Intermittent fasting as a stand-alone dietary approach is extremely powerful. It is often marketed as the “eat whatever you want and still lose weight” diet, and many people have lost significant amounts of weight successfully by doing just intermittent fasting. Although weight loss is commonly the primary reason people start intermittent fasting, it is only one of the many benefits.


The biggest benefit of fasting, or intermittent fasting, when done properly, is autophagy. Autophagy is the process or condition in which the cells in your body are clearing out and/or recycling damaged cell parts. During this process the cells also dispose of pathogenic microbes such as mold, bacteria, fungus and viruses.

Autophagy, for the most part, cannot occur while we are digesting food, and therefore fasting is the best way to stimulate and prolong this powerful cleansing and renewing process. Increased cognitive effects, longevity, anti-aging, cancer fighting, and an improved immune system are just some of the many benefits of autophagy.

Boosting Anti-aging Hormones

Human Growth Hormone (hGH) is known as the anti-aging hormone, unfortunately our natural production of hGH declines as we age. Exercise, particularly high intensity full body workouts, and proper sleep are great ways to increase hGH, but fasting is by far the most powerful way to boost hGH naturally.

Different Approaches to Intermittent Fasting

16 and 8 Intermittent Fasting

The most common method of intermittent fasting is the 16 and 8 approach, and the guidelines for this approach are as follows. Calorie consumption of any kind is restricted to an 8-hour window each day, and no calories are consumed for the remaining 16 consecutive hours. An example of this would be eating your first meal at noon, eating your last meal prior to 8pm, and then not consuming calories of any kind from 8pm until noon the following day.

Sixteen hours of fasting is generally considered the minimum amount necessary in order to capitalize on the weight loss benefits of intermittent fasting, however to trigger and prolong autophagy and the hGH boosting benefits, an 18 and 6, or 20 and 4 intermittent fasting approach is generally recommended.

24 Hour Fasting or One Meal a Day (OMAD)

Fasting for a full 24 hours is a fantastic way to extend the benefits of autophagy, and further increase hGH, but the body composition or fat loss benefits tend to diminish somewhat when fasting beyond 24 hours. Some people also find it difficult to consume all of their daily nutrition during one sitting.

Anything beyond 24 hours is generally considered prolonged fasting, which I cover more thoroughly in a different post. Fasting for 48 to 72+ hours can have phenomenal health benefits, but it requires a slightly different approach, and is usually only done periodically.

Intermittent Fasting and Keto Complement Each Other

Fasting is a great way to expedite the process of getting into ketosis initially. It also makes it easier to stay in ketosis, and encourages the use of body fat as fuel rather than just dietary fat. In order to get into ketosis, we must first lower our glycogen levels, and by maintaining low glycogen stores consistently, we train our bodies to target fat over glucose as its primary fuel source.

The following graph is from a study conducted in 2011 (reference below) examining the dynamic response of selected hormones and substrates during a 24-hour fasted period.

Graph outlining the decline of glycogen and increase in fatty acids and ketones during 24 hours of fasting

  • Solid green line = blood glucose (multiplied by 0.8 to give it a better view)
  • Solid black line = glycogen
  • Dashed blue line = plasma glucagon
  • Dashed orange line = plasma insulin
  • Dashed black line = plasma free fatty acids
  • Dotted brown line = blood ketone bodies

Reference – Xu, Ke & Morgan, Kevin & Gehris, Abby & Elston, Timothy & Gomez, Shawn. (2011). A Whole-Body Model for Glycogen Regulation Reveals a Critical Role for Substrate Cycling in Maintaining Blood Glucose Homeostasis. PLoS computational biology. 7. e1002272. 10.1371/journal.pcbi.1002272.

As you can see by the graph, the 12-hour mark is where the magic happens. At that point most of the body’s glycogen has been spent and fat burning begins to skyrocket as noted by the dramatic increase in plasma-free fatty acids and blood ketones. You can also see where fasting at least 16 hours is beneficial, but 20 to 24 hours is superior.

Through keto, both insulin and glycogen remain low and consistent. By combining intermittent fasting with keto, we are able to get into deeper ketosis, and amplify the benefits of fasting. Because we are not refilling our glycogen stores when we are on keto, we are able to reach the “magic” much earlier during our fast and capitalize on the fat burning and autophagy benefits for a longer duration each day.

How to Start Intermittent Fasting

There are several ways to incorporate and benefit from intermittent fasting, and my advice when starting out would be to take it slow. Simply start by delaying your first meal an hour or two, and slowly push it back later and later each day. It may take a little longer for people that have become accustomed to eating a large breakfast first thing in the morning but there are a few things you can consume to help ease the process.

What you Can Consume During a Fast

As a general rule of thumb, anything with calories will break your fast, and some calorie-free sweeteners can also trigger an insulin response and therefore ruin your fast. Things you can consume include the following, and I would recommend not straying too far from this list.

Water – Of course you should be drinking a considerable amount of water throughout the day, but it is even more important while fasting. Drinking water will help curb your appetite and aid in mobilizing fat and flushing out toxins while you fast. Resist the urge to use water enhancers or sweeteners as these will reduce the hydrating properties of the water and depending on the ingredients may interrupt your fast.

Coffee – The caffeine and polyphenols in coffee can actually increase cell recycling and autophagy, but it must be consumed black (no cream, no sugar, and no artificial sweeteners). I also recommend consuming only organic coffee, using pure filtered water for brewing, and a glass, stainless steel, or  BPA free French press, pour-over coffee dripper, or standard coffee maker.

Large package of Stevia SelectStevia is considered to be the healthiest natural sweetener option, and it doesn’t elicit an insulin response in most people. I personally like to add stevia, cinnamon, and a small pinch of pink Himalayan sea salt to my coffee. My go-to brand of stevia is organic Stevia Select. I buy it in bulk since it is much cheaper and I use it for other applications. Organic cinnamon is also a powerful fat burner, and it really enhances a cup of coffee, and pink Himalayan sea salt adds electrolytes and trace minerals, and reduces bitterness.

Tea – Similar to coffee, tea can benefit fasting and autophagy. Again, I would only recommend using stevia if you prefer your tea a little sweet. Green tea is particularly beneficial when it comes to weight loss and antioxidants. My go-to brand and flavor is Traditional Medicinals® Green Tea Ginger.

Apple cider vinegar (ACV) – Two tablespoons of apple cider vinegar diluted in 12 ounces of water is a powerful health booster. ACV has been shown to help reduce blood sugar, improve digestion, increase mineral uptake, and treat candida, among other things, and it won’t break your fast.

A bottle of Bragg's apple cider vinegarTo reap the full benefits of ACV it is important to use raw, unfiltered, organic ACV with the ‘mother’. I use a few drops of liquid stevia to help make it a little more palatable, and I either use a stainless straw or brush my teeth immediately afterwards with a baking soda-based toothpaste, in order to protect my tooth enamel from the acidity. ACV capsules can also be beneficial if you simply cannot handle the taste.

Note: Do not consume ACV without diluting it first as the acidity can erode tooth enamel and damage the esophagus.

Electrolytes – The body needs the proper balance of potassium and sodium for optimal health. Through active transport, sodium is pushed out of the cells in order to draw in potassium. This ion exchange creates a chemical battery that drives the transmission of signals along nerves and powers muscle contractions. These electrolytes are also important for energy production, fluid balance and proper kidney function.

Our paleolithic ancestors consumed approximately 11,000 mg of potassium daily from a variety of foods, and less than 700 mg of sodium. Today sodium is abundant in our diets due to its over use in processing and preserving foods. The average American currently consumes somewhere between 2,500 and 7,500 mg of sodium daily, and only about 2,500 mg of potassium.

This imbalance can cause high blood pressure, circulation and kidney problems, and add unnecessary stress to the heart. To help balance things out it is important to be conscious of our sodium intake, and focus deliberately on increasing our potassium intake. Green leafy vegetables, nuts and seeds, and avocados are keto friendly foods rich in potassium, but of course these can’t be consumed during a fast.

Electrolytes will not break your fast, are particularly beneficial when starting keto and can help curb the discomfort of the “keto flu” (flu-like symptoms that occur during the fat adaptation process). Most electrolyte powders are high in sodium and low in potassium, because sodium is cheap, and therefore they only contribute to further imbalance.

A container of Dr. Berg's electrolyte powderMy preferred brand is Dr. Berg’s Electrolyte Powder. One serving provides 1,000 mg of potassium (from potassium citrate) and only 10 mg of sodium (from sea salt). It also provides 120 mg of magnesium (from magnesium citrate), 75 mg of calcium (from calcium lactate), 15 mg of chloride (from sea salt), and 100 mg of ConcenTrace® trace minerals. It is also sweetened with stevia which as I noted earlier will not interrupt your fast.

I believe it is also important to note that things like bone broth and branched chain amino acids (BCAAs) will break your fast. There are a few people, even experts in keto and intermittent fasting, that suggest that a small amount of fat, cream in your coffee for instance, is OK during a fast. It will break your fast, but because fat doesn’t elicit much of an insulin response, you should return to a fasted state within a very short period.

This may be true if you are fat adapted, but I would encourage you to not add any fat during your fast if you are just starting out on keto, or intermittent fasting, or if you are struggling to lose weight.

Before You Start Your Fast

If you are already doing keto, then initiating intermittent fasting is quite easy because of the satiating effects of eating a high fat and low carb diet. If you are planning to use intermittent fasting to help initiate keto however, I would encourage you to consume a high fat, and high fiber meal the evening before starting your fast. This will keep you feeling full longer, and allow you to delay breakfast several hours without feeling overly hungry.

Quick Summary

  • The synergistic relationship between keto and fasting is a natural phenomenon that goes back millions of years.
  • Along with many other benefits, intermittent fasting supports weight loss, cell recycling and detoxification, and increases anti-aging hormones like hGH.
  • There are several approaches to intermittent fasting, but I believe the 20 and 4 method is optimal, and the one I have received the most benefits from.
  • By rapidly reducing glucose, fasting is a powerful tool to assist in getting into and prolonging ketosis and triggering autophagy.
  • Following a keto diet makes fasting easier due to the hunger curbing effects of eating high fat low carb foods, and glucose stores remain low, expediting the processes of ketosis and autophagy.
  • Eat a high fat, high fiber meal each evening to help you prolong your fast the following day and only consume water, black coffee, tea, diluted ACV, and/or electrolytes during your fast.
  • Stevia is the only sweetener I would suggest using during a fast, but I do recommend keeping it to a minimum.

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