Ketones & 72-Hour Fast
– My Cancer Journey –

Dr. Al Danenberg Nutritional Periodontist

April 11, 2021 [printfriendly]

BioSense Ketone Breath Monitor

I completed my first 48-hour, water-only fast on 3/8/21 and reported my results on my Website. In that Blog, I wrote about the benefits of fasting, cited several medical articles, suggested those who shouldn’t fast, and described my personal experience. Since I had great success, I’m making “fasting” a regular addition to my 10 Unconventional Cancer Protocols. I want to emphasize that this is a “water-only fast” with no caloric intake.

But I am extending the fast to 72-hours. The reason: There is greater potential for autophagy to occur and for the repair of dysfunctional mitochondria and damaged immune system cells during the extended fast.

In this article, I’ll summarize:

  1. The benefits of extended fasting,
  2. My way of eating,
  3. 8 phases of a 72-hour water-only fast,
  4. My 72-hour water-only fast, and
  5. My overall experience


1) Summary of Benefits of Extended Fasting

  • Improved memory
  • Better concentration
  • Reduced inflammation
  • Lower blood pressure and heart rate
  • Decreased atherosclerosis
  • Cancer prevention
  • Enhanced insulin sensitivity
  • Increased fat-burning
  • Decreased hunger
  • Anti-aging effects
  • Activation of cellular cleanup (autophagy)
  • Regeneration of weakened mitochondria and immune system cells
  • Decreased nutrient supply to cancer cells, thereby inhibiting the cancer cells’ rapid growth


2) My Way of Eating

As you may know, I primarily eat an animal-based diet along with a few selected fruits and vegetables. This way of eating keeps me in ketosis for 6 days. Then I increase my healthy carbs and cycle out of ketosis for one day. The next day I start another 6 days of ketosis. This is my method to keep my body metabolically flexible.

The human species basically existed “in” and “out” of ketosis throughout evolution. Our Paleolithic ancestors most likely ate once or twice a day. However, they often skipped eating for days when food was scarce. Skipping meals and not eating for multiple days are also typical for most animals living in the wild. As a matter of fact, ketosis is prevalent throughout the entire animal kingdom.

In addition, when animals in the wild get sick, they stop eating, enter a state of ketosis, and focus on resting. This primal instinct reduces stress on their internal system and enhances their immune system to fight infection.


3) 8 Phases of a 72-Hour Water-Only Fast

Basically, there are 8 phases that occur as you progress through a 72-hour fast. Each one ushers in a biological change in the body. However, there are many factors that influence the timing of these phases. Here is an approximation of the timeline:

  1. Your body must be prepared for this extended fast. I am prepared because I eat in a way that keeps me metabolically flexible. If you tried to do a fast and still ate an unhealthy Standard American Diet, you would not do well.
  2. Around the 12-hour mark, your body begins breaking down fat cells, releasing 3 fatty acids and 1 glycerol molecule (which the liver converts to glucose).
  3. After approximately 18-hours, your liver glycogen stores become depleted, and your liver begins to create ketones.
  4. At the 24-hour mark, your individual cells begin recycling its old components and breaking down damaged proteins. This cellular cleansing is called autophagy.
  5. About 48-hours after the start of your fast, your growth hormone level increases up to five times higher than it was at the beginning of your fast.
  6. At the 54-hour mark, your insulin levels drop to its lowest level from the start of your fast. The result is that your body is becoming increasingly insulin sensitive.
  7. By the 72-hour mark, your body has been breaking down old immune cells and dysfunctional mitochondria and regenerating new ones.
  8. At the completion of the 72-hour water-only fast, you need to begin refeeding your body gently. Remember, your gut has not been digesting food for 3 days. Don’t stuff yourself!


4) My 72-Hour Water-Only Fast

Let me describe how I integrate my fasting with my overall eating style.

I start my 72-hour water-only fast after I end a carb cycle day. In that way, I totally switch my metabolism away from using ingested carbs as a fuel source. Once my ingested carbs and liver glycogen are becoming used up, my body begins actively breaking down fat cells. Finally, my liver starts producing significant levels of ketones.

All during the fast, I’ll drink mineral water or caffeine-free herbal teas steeped in mineral water. First thing each morning, I drink 8 ounces of SOLE water on an empty stomach. SOLE helps hydration and provides 84 trace minerals. Also, during each day of the fast, I eat a little Himalayan or Redmond salt to make sure I am getting enough minerals, especially sodium. During ketosis, the human body may need as much as 6-10 grams of healthy salt daily since insulin levels are so low. SOLE in the morning provides about 0.5 grams of sodium.

I’m very geeky, and it is important for me to know my ketone levels as I progress from burning carbs to producing ketones by my liver. I use the Ketone Breath Monitor from BioSense. It is quick, easy to use, and has been proven to be clinically reliable. The data from the Ketone Breath Monitor are uploaded and stored on the company’s App on my iPhone.

I took 4 screenshots of my fasting days from this App, which I will explain in detail shortly. The 4/1/21 screenshot shows that my ketone levels dropped to “0” ACEs after my last carb meal when I began the fast. “0” means that my body is not producing ketones and is burning only glucose as fuel.  Then, the 4/3/21 screenshot shows that my ketone level slowly rose to “28” ACEs by the end of the fast. “28” means that my liver primarily is producing large amounts of ketones for fuel. (ACEs are BioSense’s scoring system for breath ketones. Essentially, if you divide ACEs by 10, you will get an approximation of blood ketones, which are reported in mmol/L units. For example, a score of “28 ACES” is equal to a “ketone blood level of 2.8 mmol/L”.)

The following Table explains the interpretation of ketone levels measured in ACEs.


Below are the 4 Ketone Graphs from the BioSense App on my iPhone for each of the days of my fast. In total, these graphs tell the story of depleting my glycogen stores, entering ketosis, and maintaining a high level of ketosis for the duration of my 72-hour, water-only fast.








I started the fast on 3/31/21 at 5 PM. The Ketone reading was “6”. It is important for me to point out that the readings on the breath monitor (measured in ACEs) lag the actual blood ketone levels (measured in mmol/L) by approximately 1-2 hours.

Around 9 AM on 4/1/21, my ACEs were at “0”. I assume this is when my carbs and glycogen stores were becoming depleted. After 9 AM, my ketone levels began to rise slowly. I probably was in ketosis and my liver was producing ketones by 9 PM as my ACEs started to rise above “5”.

On 4/2/21, I saw a steady rise in ketosis as my ACEs continued to rise to a high of “18”.

On the last day of my 72-hour fast, 4/3/21, you can see that I was in full blown ketosis with my ACEs as high as “28” at 4:30 PM. I ended my fast at 5 PM.


5) My Overall Experience

In the evening on Wednesday, 3/31/21, I ate my last carb meal at 5 PM. As usual, I felt fine and went to bed around 9:30 PM.

As I began my first full day of fasting on Thursday, 4/1/21, I felt great with slight hunger. But by 4PM, I felt very hungry. Drinking some hot caffeine-free tea took the hunger away.

On Friday, 4/2/21, I had some stomach rumbling, but no real hunger any longer and no discomfort.

On Saturday, 4/3/21, there was no desire to eat. I felt tremendous energy and clarity. The slight physical discomfort I usually experience because of my past pathological fractures was not present. I probably could have continued fasting at least another day or more. But I didn’t.

All during the fast, I had no problem with bowel movements.

Compared to my 48-hour fast last month, this was far better because of the enhanced energy and clarity by the 3rd day of the fast. And I believe my body is able to repair better on the 72-hour fast. As I said, I will continue with a 72-hour water-only fast regularly and reap the medical benefits as they have been reported in many professional journals.


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  1. Hi Dr. Al,
    Thank you for this valuable information! Do you still take your supplements while fasting?

    • No. I do not take anything except my Mineral Water during the day and SOLE first thing in the morning.

  2. Wow, congrats! Wonder what caused the drop in pain on day three? Endocannabinoids?

  3. That breath ketone monitor sounds interesting. The urine strips are massively unreliable and I just can’t face pricking my fingers multiple times a day with a blood meter. I like geeking out with data but not at the cost of finger pain.
    I agree that if you are doing 48 hours fasting, you may as well do 72. The third day is the easy one.
    Have you done any research into extended fasting, say a week or more, in regards to cancer? I have been considering this and wondering where the “diminishing returns” point lies.

  4. Do you restrict physical activity during the 72 hour fast…I golf, bike, light lifting…I am fascinated by your results

    • I only suggest light to moderate exercise. It will help preserve muscle mass and burn fats for fuel. Also, it will assist in ketone production and autophagy.

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