My first “fast” was about a year ago: 18 hours. I remember it being difficult, but a fun mental challenge—and I never thought I’d be able to fast for much longer. This morning, I completed my longest fast to date, 56 hours (2 1/3 days).
After a year, a lot has changed. 18 hours is easy now. The very first time I fasted, I got a headache about 14 hours in. On this 56-hour fast, I didn’t have any headaches, and I didn’t really notice I was hungry until hour 33 or so. (I’ve long since learned that the secret to fasting is to drink tons of water. The hydration alone makes me feel so much better during and after fasting.)
I’ve done 36-hour fasts, which have been pretty difficult. This time around, I stopped feeling hungry around hour 37 (halfway into day 2). I went on a walk in the rain, came back to the office, and felt 100% energized for the rest of the day—no food necessary.
The most difficult part of not eating for such a long time isn’t physical, it’s psychological. I want to eat and think I need to, even though my body is energized. (A large part of that problem is that I eat too much sugar, which is addictive and makes you feel like you always need more.)
Nonetheless, I felt great.
The next challenge: a 72-hour (3 days) fast.
(Disclaimer: I am not a medical professional. None of this is advice, just a report of my experience. Your mileage may vary.)