I recently completed a 42-hour fast. Last summer, I had done a 24-hour fast and found it challenging around the 24 hour mark. Extending that time, I learned a lot:
- The 18-26 hour timeframe is the hardest interval. From what I understand, this is typical, as the body switches towards fat metabolism.
- At the ~26-hour timeframe, I felt that mental clarity was excellent, and I was able to complete a project prior to going to bed with good concentration.
- Going to bed at the ~30 hour timeframe, I felt hungry but that faded and disappeared as I slept (waking up I did not feel hungry).
- In the morning at the ~38 hour mark (!), I did not feel particularly hungry so I went about my business until noon, where I decided to eat some of my freshly fermented 6% milkfat yogurt with blueberries along with a kohlrabi (low net carbs). I felt no urgency and I am sure I could have gone the rest of the day and another night. I also went for a 400 calorie bike ride about 2 PM (two hours after eating) and felt pretty good. That held me until 5 PM, when I ate a 1 pound sous vide ribeye steak and some grilled scallions, and a couple of very small oranges and a little other fruit.
- That night (after breaking fast), I was running “hot” with a higher than normal heart rate. Pretty darn hot since I woke up damp from sweat with a bedroom ambient temperature of 40°F. So my body was doing something unusual. Waking up in the morning, my body temperature was 98.3°F, which was 0.2°F higher than all previous readings for a year.
- I did not feel particularly hungry the next day. I am sure that I could have fasted again without too much effort.
In short, it looks like fasting triggered significant metabolic activity, and actually seemed to reduce appetite following the fast.
Were there any benefits? I don’t know, but I will probably do it again once a week to see if I can note any changes over a few months. I hold out the hope that fasting might influence my ongoing auto-immune issues, including autophagy of tissues that perhaps are not so great from the past two years.
Below, a serious nerd’s view on fasting.