Tonight I achieved what perhaps very few modern humans have ever done: I fasted for 48 hours. Let me share my reasons for doing so and the results.
Before we proceed, let me say that I do know that people are hungry and undernourished and that people do fast all the time. But most people have access to something edible and wouldn’t commonly refrain completely from calories for two days straight.
The reason I did this was that is some literature suggesting that fasting can regenerate the immune system by triggering stem cell proliferation. See this study showing 72-hours regenerates the immune system by down-regulating of IGF-1 and PKA (protein kinase A). There is also a vast literature suggesting that caloric restriction can enhance longevity and perhaps this is one of the mechanisms.
For the last 48 hours, I have had no calories and only taken water. Surprisingly, it was not that difficult. There was a low level of hunger but drinking water, staying busy, and sleeping was enough to distract me.
My thoughts were clear throughout and the only time I had a problem was during hour 45 when I engaged in an intense cardio routine. At about minute 35, my breath became short, my face started tingling, and I was loosing balance- probably the result of hypoglycemia.
What is it about fasting that is good for us? For one, it changes the monotony of cell life. A little variety is good. If the cells get bored and complacent, maybe your body will as well.
One concrete reason may also be that fasting allows cells to clean themselves out in a process known as autophagy. 48yo actor, Terry Crews, explains his intermittent fasting benefits in this article.
I think it is significant that certain religions proscribe fasting- perhaps they knew something. All I can say is that it wasn’t that bad and I probably lost some weight. Whether it regenerated my immune system, we shall see in the results of my next immune age test. I plan to do a 72-hour fast soon- I just had a dinner planned with a friend.
Why do we get hungry? Why doesn’t fasting hurt us? How do we produce glucose and ATP to run on? These questions can all be answered if you read my book, The Telomere Miracle: Scientific Secrets to Fight Disease, Feel Great, and Turn Back the Clock on Aging.
If you read my chapter on diet, you are sure to learn some important facts that will be useful to you. Most important is the notion of a glycemic index of foods, which will explain why we get fat. It is really quite simple: excess surges of glucose releases insulin, which stores fat. This adaptation is needed because we adapted to survive with variable food supplies and the ability to store fat for future use is very adaptive.
If you could be engineered to never get fat like these mice, would you do it? I would recommend against it as being able to store reserve calories is a useful trait. I met a young man who looked much younger than his age who might have had a similar mutation. At 5’8″, he had trouble maintaining a weight above 110lbs. Perhaps you can’t be too rich, but you can definitely be too thin.
At any rate, the reasons that fasting may be beneficial may be myriad and complex and whether it is a couple of days a month, the 5/2 (two weekly days of 500 calories or less) that has recently become popular in the UK, or Terry Crews 16 hours daily fasting, it is probably a beneficial thing, as long as you don’t have a hormonal dysregulation, like diabetes.
There is something to be gained from stress- whether it be life stress, emotional stress, physical exertion, or starvation. Science may never decode the signals of stem cells and how they respond to stress but every day, we are getting closer to decoding some of the pathways that regulate the constant birth, maintenance, and destruction of our cells that comprise our bodies.
Don’t let routines control your eating; consider the benefits of intermittent fasting and perhaps give it a try. Perhaps there more than a casual aphoristic relationship between the notion of staying hungry and staying young?
4 thoughts on “My first 48-hour fast”
I fasted for 4 days in 1981 at which point I could barely get out of bed and ate 2 1/2 chickens. I’ve never been able to do it again. But your experience sounds beneficial and maybe I could do it again.
I fasted the same way, but for 10 days. I was hungry for a day and a half, and not at all thereafter. I did it as an experiment, but no great epiphany occurred. I only started eating again because I was worried that it would be bad for my health if I didn’t.
Great article Dr. Park! I did a 72 hour fast in early September 2018. My wife and I now fast about 18-24 hours daily and do a 48 hour fast about once per month or every couple weeks. I’m down to my high school wrestling weight and have the best health of my entire life BY FAR! All sorts of chronic conditions I’ve had for many years vanished!
Yes, the fasting is great as a daily or monthly activity!