Why do I fast?

I woke up. My heart was beating 20 beats faster than usual, my body felt strong, I could hear every whisper, my sight was sharper, I felt like running. Today I could kill a mammoth!

That’s how I felt this morning, just 36 hours into my 72 hours fast.

People are often curious why would I torture myself with a prolonged fast. There are different reasons for different people — some do it for the weight loss. But with my 65 kilos, I certainly don’t. I would like to share my thinking on fasting.

The human body was designed to go without food for days. For 200,000 years, the hunters and gatherers would not catch a mammoth every day, they would go for extended periods without food. It is only the last century in which a (lucky) part of the population enjoys an overabundance of food.

Nutrition science has gained some interesting insights into what happens in the human body on the cellular level recently. Those discoveries are mainly related to mTor and autophagy. It turns out that human cells behave differently in the fasted state than in the abundance of food.

Fasting induces a metabolic switch in the intestinal stem cells. The cells go from utilizing carbs to burning fat; this state is called ketosis. Autophagy occurs during fasting to preserve cellular homeostasis by recycling proteins and organelles to produce ATP (the cell food). Damaged cells, like maybe even cancer cells, are used as energy for healthy cells. In 2016, there was a Nobel prize in Medicine to Yoshinori Ohsumi for these discoveries.

There is mounting evidence that autophagy could help the body cleanse from cancerous cells. Evidence in mouse points to that the theory about autophagy linked with longevity might be right. Fasting and ketosis are now used regularly to treat seizures. There are some interesting side effects — ketosis reduces the amount of carbon dioxide produced by the body in relation to the amount of oxygen it consumes. US Navy Seals apparently experiment with keto to improve their dive time, and also to decrease seizures.

Update 26/5/2021: There is now a great take on mTor, autophagy, rapamycin, etc by Radiolab recently. As always, amazing storytelling about how looking into the dirt at Easter island led to the discovery of mTor.

I did my regular morning swim and the difference in breathing is noticeable! Also, my sense of smell and hearing is definitely more intense.

That said, the negative effects of fasting and the keto diet are largely unstudied and might outweigh the positives. My philosophy is a balance as that is the best way to hedge your bets under uncertainty. This is why I won’t be getting into extended fasting beyond 5 days nor a full-fledged keto diet. In the end, I am betting with my life.

So, why do I fast? To wake up my inner caveman to help regenerate my body. And also, to challenge my mind and body.

I do a 3-day fast once a month followed by 4 days of the keto diet.