Learnings from my 5 day water fast, data-backed analysis and experience
By Adrian Li
I’m an entrepreneur, venture capitalist and endurance athlete get in touch with me at Adrian@convergencevc.com
My 5 Day Water Fast Experience, Data-backed Analysis and Learnings:
I’ve been an avid proponent of fasting since 2015 after reading the Eat Stop Eat book by Brad Pilon and so after 3 years of following this protocol on a weekly basis I was curious to try an extended fast. While the 24 hour fast was effective for weight loss based on my reading some of the additional benefits of fasting such as cell regeneration, ketosis and immune system reset appeared to come only from extended fasting. Why 5 days? As you’ll see below over 3 days of fasting seems to be the trigger point for many of the aforementioned benefits.
What is Fasting?
Fasting is simply the voluntary abstinence of food. It can last from several hours to many days. While there has recently been a lot of news covering “intermittent fasting”; fasting has a long history. It has been practised by many religions in various formats since the dawn of society and it has also been used therapeutically by early doctors such as Hippocrates and Paracelsus who wrote, “Fasting is the greatest remedy — the physician within.” However it has only been in recent years that medical researchers have started to review in depth the biological benefits of fasting.
What happens when we fast?
When we eat our bodies produce the hormone Insulin which is needed for two key processes in our body. First for cells to absorb glucose from eating for energy, second for excess energy from eating to be stored in the liver and then later as fat when liver stores are full. When we fast, this process is reversed. Insulin levels go down and our bodies start converting stored glycogen into glucose for our bodies to use. Essentially the body goes through a series of states as described by George Cahil one of the leading experts on fasting:
Source: Cahill, “Fuel Metabolism in Starvation”.
1) Feeding: blood sugar rises as we absorb food. Insulin rises to move glucose into cells and excess is stored as glycogen in the liver or converted to fat.
2) Postabsorptive phases (6–24 hours starting to fast): blood sugar and insulin levels fall. The body starts to burn glycogen and releasing glucose. Glycogen stores last about 24–36 hours.
3) Gluconeogenesis: 24 hours to 2 days from the start of fasting glycogen stores have run out. The liver now manufactures new glucose from aminoacids.
4) Ketosis: (2–3 days from starting to fast). Low insulin levels stimulate lipolysis, the break down of fat for energy. Triglycerides are broken into their components with glycerol for gluconeogenesis and the fatty acids used for energy by other parts of the body. The body also uses fatty acids to produce ketone bodies used for the brain for energy. The two major types of ketones are beta-hydroxybutyrate and acetoacetate. This is also the time (when glycogen levels in the liver are low that autophagy is triggered).
5) The protein conservation phase: high levels of growth hormone maintain muscle mass and energy for metabolism is almost entirely supplied by fatty acids and ketones.
What are the health benefits associated with fasting?
Research has shown that fasting is associated with a number of health benefits that can prolong life and offset certain diseases.
Weight management: This is an obvious one. But what is not as intuitive is that while a diet of fewer calories has been shown to result in lower metabolism; a fast can actually increase metabolism. Given the body relies on body fat for fuel once readily available glucose is spent, this can be an effective way to reduce unwanted fat.
Diabetes:There is a lot of research to show that fasting decreases blood sugar levels and can reverse insulin resistance. Prolonged high blood sugar levels can lead to Type 2 diabetes which is one of the leading modern health issues. Decreasing insulin resistance makes your body more efficient at transporting glucose help keep blood sugar levels steady. Fasting glucose and fasted insulin measures are both markers which can assess this.
Promote health through reduction of inflammation: While acute inflammation is normal to fight off infections; chronic inflammation can have negative health consequences leading to heart disease and cancer. Leukocyte count correlates positively with genuine markers of systemic inflammation like C-reactive protein and interleukin 6. Interestingly, some authors conclude that leukocyte counts even have a stronger prognostic ability with regard to total and cardiovascular mortality than total cholesterol or low-density lipoproteins.
Cardiovascular Disease: Heart disease is the leading cause of death around the world contributing to 31% of deaths. Fasting can lower levels of cholesterol and blood triglycerides which have been shown to have a correlation to heard disease. Both cholesterol and triglycerides can be measured to test this.
Brain Health: A number of animal studies have shown that fasting can ward off development of Alzheimer’s disease and Parkinson’s however these are still in an early stage. This research is predominantly linked to the reliance of energy from Ketones once ready available glucose is used up which is a state that happens after 24–36 hours of fasting. One marker that can show evidence of this is the level of Ketones in the body.
Longevity:There is a lot of research in animals to show that restricted caloric intake correlates to longer life. While clinical evidence in humans is scarce we can look to Okinawans who generally at to only “80%” and who have the longest life expectancy in the world. Some of the contributing functions from this comes from autophagy which happens after 36 hours of fasting which is when the body breaks down cells which are not fully functioning (and may later become cancerous) for reuse. One marker for this is the production of uric acid from the body which arises from this mechanism.
The 5 day water fast
I decided to begin the fast the day after new years eve. Not only could I work off some of the holiday season excesses but the beginning of the new year is generally a quieter period for work and meetings so I could have greater control on my schedule. So this wasn’t a completely 100% strict water fast, during the day I allowed myself to have black coffee and green tea. In addition, I also incorporated a single bowl (250Ml) of bone broth each evening in order to have some continued input of salts. As the total calories from this is approximately only 35cal I felt this would not impact the results of the fast.
Day 1: was very much the same as my usual Monday when I do 24 hour fasts with the exception that I didn’t eat dinner. What I was surprised about was that I still managed to sleep easily. From dinner on however I was entering uncharted territory.
Day 2: I was up early before 6AM. I noticed that my RHR went down to 52 (using Fitbit) and that overnight it was mostly in the 40’s range. The day went by smoothly with no signs of headache, weakness or excessive hunger. I had 300Ml of bone broth and went to bed at 9:30.
Day 3: Over night I woke several times feeling a little restless and also warmer. I woke early again at 5:30AM and had to head to Singapore for a days worth of meetings during the day. During the day continued drinking water and some green tea until I got home in the evening for my usual broth.
Day 4: I woke at 6:15 in the morning and head a reasonably good sleep. However I’m now feeling like I’m really missing eating. Not so much the hunger however it’s literally the sensation of eating. I started dreaming about all types of food. By the time we got to the evening I found it quite difficult as I sat around the table watching my kids eat. Also just thinking about being able to eat the next day was torturing me.
Day 5:I headed off to the clinic to do my blood test prior to breaking my fast in the evening. I was at home around 11am when I had a very concerned lab technician call me to say that one of my readings — my uric acid count had gone through the roof! Having a family history of Gout (my father and youngest brother both had attacks and I have elevated levels already) I was quite concerned I may trigger an attack so I decided to end my fast at 113 hours and 20 mins.
The Data:
Analysis & After thoughts:
Overall I found the water fast challenging but quite achievable. I’m sure regularly fasting since 2015 contributed to it being a more tolerable experience however having the right mind set certainly helped. What was most fascinating was interpreting the data that I received from the 3 blood tests; before, on the last day and 5 days after completing the fast.
Body weight and fat loss: The obvious benefits came from rapid and sustained weight loss. What is interesting is that out of my 2kg total weight loss I appeared to lose a sustained 1.2–1.5kg of fat. Based on my metrics I would have a Basal Metabolic Rate of around 1,500 cal and probably burn around 2,000 calories over the day with light exercise/walking. If glycogen stores were fully depleted after 24 hours that would mean I would need to burn approximately 7,416 (2000 x ((113–24)/24) calories from fat during the fast. 1KG of fat is about 7,000 calories which would suggest about 1.059 KG of fat (7,416/7,000). This looks a little shy of what my calculation shows below. However if we take into account studies which show that fasting increases BMR by 14% this could account for the difference almost exactly. (1.059 x 1.14) = 1.21KG over the 5 days. I also appeared to continue to burn fat more efficiently even after resuming normal eating hence more fat loss 5 days after the fast finished (but granted this does not control for water % although I did weigh myself at the same time each day.)
Blood Sugar: I was most interested in this marker because I had previously been cautioned about my high fasting glucose and was also being close to the pre-diabetic reference range. Here I found quite a dramatic change both in fasting glucose and fasting insulin and helped confirm my belief that intermittent fasting can have a significant effect on fasting glucose and insulin.
Cardiac Health: I was surprised by this one as short term fasting actually increased both my cholesterol and triglycerides. This may sound contrary to contributing to heart health however it could be linked to the release of triglycerides for supplying energy. Interestingly, there does not appear to be a lot of research on this area. Having said this, later tests showed my markers going back down to normal levels. Any pointers to research explaining this short term phenomena would be appreciated.
Inflammation, Liver Function and Uric Acid:
I was curious about some other markers which changed significantly during and after the fast and picked up on these. While I do not have a medical background I conducted some internet research to find explanations. Leukocytes appears to be a marker for inflammation. Hence the reduction in this correlates to one of the benefits of fasting. My understanding is this is also associated with lower levels of glucose and insulin during a fast.
SGPT is a market for liver function, higher values are associated with damage to the liver or potentially an indication for fatty liver. I regularly drink alcohol (on average half a bottle a week or so) which may have contributed to my relatively high reading pre fast. However, this marker came down during and after the fast.
Lastly, my uric acid count went sky high at the end of the fast. This one took me by surprise given I was not eating anything but researching online I found that there could be two key contributing reasons. 1) Autophagy, when the body starts breaking down improperly functioning cells after day 2 uric acid is a by product of catabolic cell death hence increasing levels in the blood. 2) When the body produces ketones the kidneys appear to process this over Uric acid leaving to a build up of uric acid in the body. While these levels went down 5 days after the fast and I did not have any gout attack the side effect of high uric acid when fasting has led me to be concerned extended day fasting.
Parting thoughts:
I’m convinced that fasting has benefits to my health and overall my blood markers support this. My main concern is around the uric acid build up but this appears to have resolved itself within 5 days after resuming eating. I’d like to make this part of an annual routine to help give my body a break from eating but it would be great to see further published research on how the blood markers change from fasting. Fasting is a relatively straight forward self experiment so if any one else tries this it would be good to see more datapoints on how it affects different people’s blood markers.
Sources and research:
https://thefastingmethod.com/fasting-and-lipolysis-part-4/
https://www.ncbi.nlm.nih.gov/pubmed/29064542
https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156
https://pdfs.semanticscholar.org/a8bb/8327226d35259e68ecd8edcc17a3a1380f4a.pdf?_ga=2.129923276.1552037844.1582442874-1716194611.1582442874
https://www.healthline.com/nutrition/intermittent-fasting-metabolism
https://www.mdmag.com/journals/internal-medicine-world-report/2011/summer2011/cholesterol-levels-rise-after-a-24-hour-fast
