The 72-Hour (3 Day) Fast Experiment: Here's What I Learnt

10 day fast shows how body switches to Ketones from Glucose as primary source of energy.
Source [HERE].

I absolutely love eating. There's nothing better than sitting down, munching on food and getting fat. It's pure joy. It is what makes me want to get out of bed and go to work. Just so that at the end of day, I would have the fulfillment of having worked hard to have earned a meal (aka that-Dopamine-hit). 

Not just any meal, a solid good meal, at a solid good restaurant. 

Our ancestors though, didn't have that luxury. They ate when they found food during the hunter and gathering era and starved when they didn't have any. Millions and millions of years of evolution forced the body's metabolism to slowly adapt. Those who couldn't, perished. Those who did, lived to see another day, mate and continue their lineage. 

Then came the age of abundance. When humans learned how to seed. When humans learned how to grow crops. Hunting and gathering was now a hobby rather than a necessity. So did the structuring of how we ate and drank and ate again. Cultures developed breakfast, brunch, lunch, tea-break, dinner, post-dinner, you name it. The cultures that didn't, were left behind, often tagged as backward, poor. Obesity showed opulence, abundance. Lose weight in Nepal and people will still think there's something inherently wrong with you. 

Along the way, our diet changed too. From primarily getting energy from proteins, fats and natural sugars from wild berries, fruits and raw, organic meat to a carbohydrate, sugar and processed food based diet that primarily derived energy from glucose. 

Glucose. Sugar. Fructose. Glucose. 

We all grew up in that culture, not once questioning whether that was actually the correct way. 

There were, fortunately, the few wise who understood how biology worked. How our intrinsic bio-clock functioned and how that affected our way to metabolize food. Those few wise used the leverage of religions to enforce people to fast and mimic diet of our ancestors. You see tradition of fasting in Hinduism, Christianity, and most notably in Islam where a whole holy month of Ramadan is dedicated to controlled, time restricted, intermittent dry fasting. As time went by, many stopped questioning why we fast and instead followed what everyone did. 

Just like sheeps. 

Science has shown, empirically, that controlled fasting has had long term health benefits [HERE] including "that promotes the growth of neurons [and] the formation and strengthening of synapses" in the brain [HERE], accelerating generation of new cells, reducing risks for cancer by starving cancer cells and most interestingly, delaying aging. 

But how?

Enter Ketosis. The state when the body's primary energy source switches from glucose and proteins to fat. Yes, that same ugly fat we think of. What fasting does is basically restrict the amount of food that goes into the body. Laws of thermodynamics and bio-chemistry forces the body to burn energy to survive and keep cells working round the clock. Since no potential chemical energy (food) is coming in, the body then relies on the liver's glycogen storage to maintain blood sugar levels. Think of glycogen as the backup generator. Once that depletes, the body then has an option to turn to proteins in muscle mass or fat storage. 

Timothy Ferriss, the author of 4-Hour Body, did an experiment where he found that after undergoing a strict fasting for an extended period of time with highly restricted movements, he lost a lot of muscle mass. However, when he instead went normally about his day and worked out while fasting, he lost a grand total of 0 muscle mass while losing weight.

What he realized, when taking measurements was that, if the body maintained normal activity during fasting, he was using his stored fat to keep him going. Basically, during such normal activity fasts, there comes a state where the body starts producing Ketone bodies and enters the state of Ketosis. Ketones is another fancy name for glucose, but those glucose derived from fatty acids after going intense gluconeogenisis. The answer to when exactly the body changes depends on person to person and could be anywhere between 48-hours to 72-hours. It is when your body is in this state for a certain extended period of time that it starts repairing cells and growing new neuron networks in the brain.

The chart below shows that the blogger from Quantified Body empirically measuring his Ketone level in blood went into ketosis right on Day 2. You will notice a nice switch between blood sugar levels and Ketone levels.

Data from [HERE]
Read his full report on the 5-day fast [HERE]
Read his full report on the 10-day fast [HERE]

As for me, I just wanted to see if I could go without eating for a couple of days. I would have wanted to take blood tests everyday but that's too 1) expensive 2) much work. Besides, I was testing my self-discipline to see if I would end up ordering a non-beef whopper at Burger King the moment I declared to everyone that my fasting had started.

One burger please. Would like a glass of 500 calorie beer too.

For your pleasure, here's my daily log:

LOG DAY 1: [10:02 PM]
Ok sooo, I have gone a full 24 hours without eating. The first day is usually easy going without food. The only issue is that you notice food more often when it's around. Like you never noticed that week old cookie on top of the table before fast. Now it feels like it's staring at me with all its might. Stupid Cookie. No signs of dizziness, rehydrated and I have this weird confidence that I will make it through the next 2 days.

LOG DAY 2: [10:20 PM]
F**k confidence. Much harder. Last time I did a 48-Hour fast, I nearly gave up on the 47th hour. Does show some progress. I did all the normal walking-to-the-office-and-back thing. The worst part was having to go through the street food market with fried chicken and steaming dumplings and all those nasty deep fried carbs. I haven't even started how good that local bakery store smelled. Definite dizziness as expected, as my glucose level should have spiked down after running low on glycogen. All I can say is that I feel drained. 

LOG DAY 3 [11:45 PM]
The first thing I did right after I hit the 72-Hour mark was to gulp down a cold glass of shitty beer. Your social life does take a big hit during these fastings. You have to plan things ahead, clear out the schedule and say no to beautiful exercises like going out to drink, eat fried meat and talk nonsense. The good life. 

Felt drained and low on energy throughout the day. Had a hard time coming back while walking on the sun. Add band practice to that. But felt good at the end of the day. I mean felt really good an hour before I ended the fast. New sort of energy? perhaps. It's likely that I could have gone into Ketosis. No way to prove that besides being anecdotal.

A four day fast awaits me next month. Can't wait.


  1. Some other preliminary results from animal studies showed time restricted feeding to protect against obesity, high insulin levels, fatty liver disease, and inflammation. intermittent fasting 16 11


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