What 72 hours without food actually felt like — hour by hour
Hour 14 was fine. Hour 31 was not. This is the complete log of my longest fast yet, written as it happened — and the one mistake that made hour 50 harder than it needed to be.
I’ve done dozens of 24-hour fasts. They’re easy now — skip dinner, skip breakfast, eat lunch. But 72 hours had sat on my list for two years, and I’d kept finding reasons not to run it. This August, I stopped negotiating with myself.
The rules I set: water, black coffee, electrolytes. No bone broth, no “fasting-mimicking” bars, no loopholes. And a full log — every few hours, whatever I noticed, written down before I could edit it into a nicer story.
01The first day is a formality
If you can skip breakfast without drama, day one of a 72 is a formality. The interesting part of any long fast is not the beginning. I worked, trained lightly (30 minutes, zone 2, nothing heroic), and went to bed slightly hungry and slightly smug.
- [■] Hour 0–16 — Normal. Mild hunger waves, gone in minutes.
- [■] Hour 22 — Best focus of the week. Wrote 2,000 words.
- [■] Hour 31 — Woke at 4am, wide awake, slightly cold. Not fun.
- [ ] Hour 48–72 — logged below, with the mistake.
Run This Protocol 0 of 5 complete
02The mistake
On day two I went to the gym. Not a hard session — but I trained fasted, in the afternoon, having drunk maybe a liter of water all day. By hour 50 I had a headache that felt structural. The fix was embarrassingly simple: salt. I’d been drinking water without electrolytes, flushing out what little sodium I had left.
The fast wasn’t hard. My logistics were hard. There’s a difference, and it took me 50 hours to learn it.
After a pinch of salt in every glass, the headache left within the hour. Energy returned. Hours 55 to 70 were, honestly, the clearest I’ve felt in months — which I say cautiously, because clarity near the end of a fast is also exactly the state in which people make grandiose claims about fasting. I am making none. I’m reporting a log.
By hour 48 my heart rate had dropped to a resting average of 52 bpm — down from the mid-50s at the start of the week.
03Breaking it
I broke the fast the way I now always do: something small, warm, and boring. The last time I broke a long fast with a burger, I wrote a whole post about the consequences. Learn from my mistakes — it’s cheaper than making them.
Would I do it again? Yes — quarterly, maybe. Is it for everyone? I have no idea. I’m one body, n=1, and this is a notebook, not a prescription.