The 72-Hour Fast I Failed at Hour 54 (And Why I Am Glad I Did)
I started the fast on a Thursday at 8:00 PM because I am an idiot and I thought the weekend would be easier. I had done 24-hour fasts. I had done 36-hour fasts. I had read the research on autophagy and insulin sensitivity and growth hormone spikes. I had a spreadsheet. I had a plan. I had electrolytes. I had no idea what I was getting into.
Hour 12 was fine. I woke up Friday morning and I was not even hungry. I had black coffee — which breaks a strict fast, but I am not a purist and neither is my metabolism. I went to work. I am a data analyst at a fintech startup in Austin. I stare at spreadsheets for a living. Fasting should not affect spreadsheets. But it does.
Hour 18 was when the hunger started. Not stomach hunger. Brain hunger. I was in a meeting about quarterly projections and I could not focus on the numbers because my brain was screaming about pizza. Not good pizza. Bad pizza. The kind of pizza you get at a gas station. My brain had lowered its standards dramatically.
Hour 24 was the ketone high. I felt amazing. I felt sharp. I felt like I could see through walls. This is the thing people talk about — the mental clarity, the focus, the energy. It is real. It is also temporary. And it is dangerous because it makes you think you can keep going forever.
I made it through Friday. I went to bed at 10:00 PM feeling accomplished. I had done 24 hours. I was one-third of the way to my goal. I fell asleep easily — fasting actually improves sleep onset for me, probably because my body is too tired to protest.
Saturday morning, hour 36, was when it got hard. I woke up at 6:30 AM and I was cold. Not just chilly. Cold. My hands were ice. My feet were ice. I checked my Oura ring: my body temperature had dropped 0.8 degrees below baseline. This is normal during extended fasting — your metabolism downregulates to conserve energy. But knowing it is normal and experiencing it are different things. I put on two sweaters and I still shivered through my morning coffee.
Hour 42 was the emotional dip. I was irritable. I snapped at my roommate for leaving a dish in the sink. I snapped at a driver who cut me off on I-35. I snapped at a spreadsheet for having a circular reference. I was not myself. I was a version of myself who had not eaten in 42 hours and whose brain was running on ketones and spite.
Hour 48 was the wall. I was supposed to feel accomplished — two full days. But I felt terrible. My energy was gone. My focus was shot. I was lightheaded every time I stood up. I had been taking electrolytes — sodium, potassium, magnesium — but I was still dehydrated. I had lost 4 pounds, which was almost entirely water and glycogen. My muscles looked flat. My mood was dark. And I started asking myself: why am I doing this?
I did not have a good answer. I was not fasting for a medical reason. I was not fasting for a religious reason. I was fasting because I wanted to prove I could do it. Because I wanted the autophagy benefits. Because I wanted to tell people I had done a 72-hour fast. And those are not good enough reasons to feel miserable.
At hour 54 — Saturday night at 10:00 PM — I broke the fast. I made bone broth. I drank it slowly. Then I had an avocado. Then I had some scrambled eggs. I did not binge. I did not eat a pizza. I re-fed carefully, because I know the risks of refeeding syndrome. And I went to bed feeling relieved, not defeated.
Here is what I learned. Not about fasting — I already knew the science. I learned about my own limits. I learned that willpower is a finite resource and that using it to starve yourself for three days is not necessarily a virtuous act. I learned that feeling terrible is not a sign that the fast is working — it is a sign that your body is asking for something you are refusing to give it.
I still fast. I do 16:8 most days. I do 24 hours once a week. I might try 48 hours again someday. But 72 hours? Not for me. Not right now. Maybe not ever. And I am okay with that. The goal of health is not to prove how much discomfort you can endure. The goal is to feel good, function well, and live a life that does not revolve around your eating schedule.
I deleted the spreadsheet. I threw away the electrolyte packets I had bought in bulk. And I went to Veracruz All Natural for breakfast tacos on Sunday morning. Migas. Two of them. With extra salsa. And I did not feel guilty. I felt fed.
— Ryan, from Austin, where the fasts are shorter and the tacos are non-negotiable.
