Prolonged Fasting

Ketosis

By late into Day 2, a significant shift from the more common state of glucose metabolism into significant fat metabolism occurs. This involves breaking down your fat stores (and the fat you’re eating if doing a vegan ketogenic FMD) into ketone bodies. One of these you burn readily is beta hydroxybutyrate (BHB). 

BHB has known anti-aging powers. It is a signaling molecule to activate longevity gene pathways. Thereby it increases cellular  repair processes, delays age-related diseases progress, and reduces mitochondrial damage (a harmful byproduct of glucose metabolism).

Increase of Sirtuins

These enzymes also activate longevity genes. They too seem to be elevated as a result of the decline in IGF1 during a prolonged fast.

Autophagy

After Day 3 your growth pathways (IGF1 and MTOR) have virtually shut down. This may sound bad on the surface and it may be so if extended too long. However, it results in some major cellular house cleaning through autophagy. This is an amazing process which can actually be seen happening under an electron microscope. Vacules called autophagosomes team up with digestive organelles called lysosomes. – Together, they consume and digest damaged and toxic components in cells and recycle them. They take damaged organelles, viruses, bacteria, and aggregate proteins, break them down and convert them to components for renewing the cell. It’s like a cellular detox.

“auto”= self, “phage” = to eat

Apoptosis

This process is always occurring in the body to some extent, but we know it is amped up significantly during prolonged fasting (72+ hours). It is actually like pre-programmed cellular suicide of those which are pre-cancerous, malignant, or badly infected. It happens in such a way that no surrounding cells are harmed. Another incredible self-preservation mechanism our bodies have.

Stem Cell Activation 

Once you starting refeeding is when the real magic happens. All of the sloughing of damaged and infected cells seems to trigger cellular renewal. This happens through the activation of stem cells and, in turn, the production of new young cells for your organs (heart, liver, immune system). Again, because of their faster metabolism, it is a particularly dramatic observation in mouse studies. Organs actually shrink and regrow with new cells. In humans, Dr. Longo comments this activation could be the most powerful organ regeneration program possible after our birth. Beyond anti-aging, it yields amazing potential for curing disease used in parallel with other medical treatments.

HOW DID I START PROLONGED FASTING

My Personal History with Prolonged Fasting

My first 4 personal trials with this were of the FMD variety. I knew I could get through the first 24 hours from my various intraday IF practice using a 20-22 hour fasting window. However, I was very concerned about being able to function in life on Day 2 and beyond with no food whatsoever.

As I had absolutely no medical conditions and consider myself in exceptional health, I did not seek MD guidance. I DO NOT ADVISE, CONDONE, OR RECOMMEND THIS FOR OTHERS. I have a few clients who are MDs and knew I was doing a prolonged fast who were unphased by it. 

I looked into buying the Prolon FMD package, but it was $250USD, and… I’m cheap. So I decided to create a DIY version. Basically, the first time I just took my normal eating program, veganized it (like Prolon is), and ate much smaller and calorically measured portions. I otherwise NEVER count calories as I don’t find it a sustainable practice. I made it through 72 hours and had 2 small meals each day within my normal 8 hour eating window. Day 1 I consumed about 1000 calories. Days 2 and 3 were around 750.

My subsequent 3 seasonal prolonged fasts were similar in the first year. However, I was able to make it 5 days for all of them. Also, I adjusted my vegan macronutrients to a ketogenic ratio (2:1 Fat : Total Carbs + Protein in grams). I was bent on achieving deep ketosis and monitored my glucose:ketone index (GKI) daily with a blood meter. 

The meter measures BHB and glucose in millimoles per liter. I used the Precision Lifestyle Glucose/Ketone Meter by Abbott Labs. You just change strips and can use blood from the same finger prick for both readings. (Note: In the US blood glucose is measured in mg/decaliter so there is additional conversion factor required: 1 mg/dL = 0.0555 mmol/L)

GKI < 9 = Mild Ketosis (for me this happened in Day 1)

GKI < 6 = Moderate Ketosis (for me this happened in Day 2)

GKI < 3 = Deep Ketosis (for me this happened in Day 3)

The past 3 prolonged fasts I bit the bullet and went for 7 full days with no food, A LOT (4+ liters) of water, and some supplementation. I did only mineral supplementation the most recent fast and added some essential vitamins the 2 previous.

Water fasting was actually easier for me than trying to worry about counting my olives and romaine lettuce leaves everyday. It was quite a freeing experience in many ways. Don’t get me wrong, every single fast was challenging. Days 2 and 3 are always the hardest from a hunger perspective. Thereafter, you still “miss” food because it’s such a pervasive part of our lives in general. However, for me there was no real hunger after Day 3 and I experienced incredible productivity and even euphoria during the back half of the water fasts.

All of this is only MY experience. As with all protocols in the realm of physiological adaptation, individualization is crucial. Right or wrong is not as important as recognizing differences in people.

WHAT HAPPENED ON MY PROLONGED FAST

I started my most recent prolonged water fast at 10:30 PM on July 30 and broke the fast 175.5 hours later at 6:00 AM on August 7. I like to break the fast with breakfast as it fits better into my normal circadian rhythm and daily TRE window.

Hydration

Starting with a 1 liter of water every morning, I typically go through a gallon or more per day. This would include still, carbonated, and an occasional squeeze of lemon or lime (purists, judge if you will). I want to be getting up to pee every 90 minutes or so. With your body fat as your primary fuel source, the toxins stored there are also released into your system. Boosting hydration helps clear these and reduces the early hunger pangs.

Mineral Supplementation

I only supplemented minerals this time to help with electrolyte balance given the massive water intake. I would add a half teaspoon of sea salt to 500 ml of water 5-6X per day (for sodium). I would also add a quarter teaspoon of cream of tartar (baking section of the grocery store – non-caloric) to 3-4 of the sodium solutions. Finally, I would take 400-600 mg of magnesium bis-glycinate (as normally) 30 minutes before bed.

Training

“Do you still workout?” This is the most commonly asked question when I discuss my fasts with people. I have tried all types of workouts I felt competent to get through while water fasting. 

Understandably, HIIT workouts which require predominantly glucose metabolism (the anaerobic glycolytic system), are absolute HELL to get through. You just don’t have the glycogen stores to work with anymore after Day 1. For this reason, I rarely try them. If I do, I make them very short (like 1 Tabata Round) and moderate the intensity without any guilt whatsoever. Because of my postoperative state, I did zero HIIT workouts in the most recent fast.

A workout type I could normally do during a fast, but not this time due to my recent surgery is pure heavy strength training. That is 3-5 short sets (maximum 5 reps) of functional lifts I’m proficient at with full recovery (3 minutes between sets). This workout uses the very short term ATP-PC energy system (no glucose or ketones required). The long rest interval enables full recovery. I have read this type of training can protect you from muscle loss due to gluconeogenesis (converting protein to glucose for your brain’s requirements). To be honest though, I’ve personally noticed little to no significant muscle loss during my longer fasts.

The final type of training which I was able to do this time was Zone 2 aerobic training. Essentially it’s conversation-pace work that didn’t push intra-abdominal pressure at all and disturb the healing of my abdominal wall. So I was just walking up a hill or cycling easy. It’s boring as all hell, but doable and kept me sane.

Please Note: “Women do not respond to fasted training in the same manner as men. Women do not have an increase in oxidative activity (fat utilization) of the muscle as a result of fasted training, but do incur a greater post-exercise immune stress and greater post-exercise inflammation as compared to men.” (These are the words of Stacy Simms, Ph.D.,exercise and nutrition science expert and author of the book, “Roar”.)… So women may do better performance-wise  with TRE and breakfast before and after training in their day AND should be VERY cautious of considering a prolonged fast.

Sleep

As in all previous prolonged fasts, I struggled with sleep the first couple of nights, but slept amazingly well the remainder of the fast. 

Fasting is a significant physiological stress which can push stress hormones like cortisol. This can suppress your immune system and interfere with sleep. I have found taking 200-400 mg of phosphatidylserine (2-4X PS-100) with my magnesium supplement before bedtime helps immensely. It is a supplement for improving cortisol levels. It may just be a placebo, but I don’t care. Honestly, on the back half of a prolonged fast, I’m exhausted at the end of the day and sleeping is typically great for me.

Ketosis

Here are pictures of the glucose/ketone meter screen for my testing on Day 5, 6, and 7. On Day 7 I reached my all-time high of BHB of 6.5 mmol/L and all-time low GKI of 0.40. For me, there is something very satisfying about metrics during any challenge.

Body Mass and Composition

I typically weigh between 150 and 155 lbs depending on my state of training and hydration. I don’t care too much about body composition with this process, but have marked its significant change in previous trials. 

I did not do a baseline weight this time, but here is a picture of the scale on Day 7. I took no body composition measurements or skinfolds either. However, I don’t feel like l have been this light or lean since college. Since refeeding, I’ve back up just under 150, and feel fantastic in my training, energy levels, and healing from my surgery.

Refeeding

In my 7 fasts, I’ve screwed this up just about every way possible. At the end of it you are not necessarily hungry, but more yearning for food. You miss it and your body (and microbiome) is crying for nutrients. However, your gut is raw and unexposed so requires gradual nurturing back to your normal eating habits. 

My normal eating program is quite void of anti-nutrients that may drive inflammation or gut damage. However, in my post-fast mindset, I have come out of the gate like a 20 year old athlete on a full-blown cheat day. The results are disastrous. In fact, most of what is consumed is almost immediately shot through. It’s gross and likely undoes many of the benefits of the process.

The first meal is crucial. I aim to have some very small but controlled levels of carbs and fat. This prevents a big insulin jump. Also, I avoid too much fiber (especially insoluble) to be gentle on the cilia of my intestinal wall – so NO salads. Finally, to keep it moving slowly through my system, I have a small serving of lean protein to slow digestion. 

This time I had a 4oz piece of cod, some nori strips, a rice cake, and 3X 1 g omega 3 supplements. It tasted AMAZING! The next meal was only slightly more adventurous and still not too large or fibrous a few hours later. 

Despite temptation, going gradually with refeeding is key for me. 

FASTING IS NOT FOR EVERYONE

As you likely understand now, prolonged fasting has loads of potential for complications. For this reason, if you are considering trying it, PLEASE SEEK MEDICAL CLEARANCE AND SUPERVISION. I am NOT a doctor or medical practitioner. I only follow a bunch of them in social media for information.

In particular, if you take any regular medication or are managing any chronic medical condition, seek MD guidance.

Finally, men and women respond to all forms of fasting differently. If you are a female athlete (or even just train like one), trying to get pregnant, pregnant, nursing, in adolescence, or perimenopausal, any fasting period longer than 12 hours is likely ill-advised. Even then, a healthy female reproductive system is crucial to female health. Any extended periods away from glucose metabolism may result in down-regulating necessary hormones for this. So even a ketogenic diet may not be appropriate for a woman in any of these stages of her life. With that said, again, individualization for everything is key. Work with your healthcare practitioners to map out a program for YOU.

OTHER REFERENCES

Calorie restriction and aging: review of the literature and implications for studies in humans

Calorie Intake and Aging

Dietary Restriction and AMPK Increase Lifespan via Mitochondrial Network and Peroxisome Remodeling 

Calorie Restriction and Fasting Diets: What Do We Know?

The effect of fasting or calorie restriction on autophagy induction: A review of the literature

Role of therapeutic fasting in women’s health: an overview

Article on Fasting for Women – Part 1

Article on Fasting for Women – Part 2