A weekly long fast: is it too much, and can you keep it up?
A 36 or 48 every week can absolutely be sustainable. What isn't sustainable is grinding the same hard protocol into the ground without a break.
You've been doing a 45 or 48 hour fast once a week for a month now. You feel great, the results are showing, and then the quiet doubt starts. Is this too much? Is it actually sustainable long-term, or am I going to pay for it? And am I just undoing the whole thing when I finally sit down to eat?
I've asked myself every one of those, so let me walk through them honestly.
Yes, it can be too much. Here's what that looks like.
There's a version of this that goes too far, and I know it because I lived it. At one point I was running 65-hour rolling fasts, one after another, and the first month was the best fat loss I'd seen in the whole journey. The second month was still good. Then in January everything just stopped. The scale stuck, the fat loss stalled, and I was running the protocol perfectly, by the book.
I could have blamed the protocol and pushed harder. Instead I looked at all five pillars, not just nutrition, and the problem wasn't the food. It was stress. Twenty-six straight cycles of 65-hour fasts, no breaks, no variation. Mentally it had started wearing me down, and physically my body was defending, chronically stressed by a protocol that used to feel fine. That's when I had the hypoglycemic event that put me on the floor.
The plateau wasn't a nutrition problem. It was my body sitting in conservation mode, defending against what it now read as a threat. So here's the real answer to "is this too much." Fasting is a stressor. A good one, but a stressor. The tell that you've crossed the line isn't the fast itself, it's the combination of a stubborn plateau plus feeling worn down by it. When those two show up together, that's the signal.
Sustainable is a rhythm, not a maximum
The fix wasn't to quit. It was to switch back to alternate-day fasting, shorter windows with more frequent recovery, and immediately everything improved again. Fat loss resumed, energy came back, sleep improved.
That's the whole game with a weekly long fast. Sustainability doesn't come from the biggest number you can white-knuckle. It comes from finding the length that does the job for you, then being consistent with it over weeks, on a rhythm your life can actually hold. Once or twice a week, not every day. And you don't have to run the exact same protocol forever. Rotating it, a stretch of weekly 48s, then a stretch of alternate-day, keeps your body from fully adapting and keeps the stress from compounding. Change one variable, keep the rest steady, and watch what happens. That's how you break a plateau without breaking yourself.
So a weekly 36 or 48, held for months with real recovery in between, is not too much for most healthy people. Twenty-six back-to-back 65s with no recovery was. The difference is the recovery, not the willpower.
The refeed worry
The last piece of your question, whether you're undoing it when you eat. Mostly, no. The bounce on the scale after you refeed is largely water weight, not fat regained. Where it can actually work against you is if you come out of a long fast and overeat a system that's been resting. So the fast isn't really the hard part of a weekly rhythm. Coming out of it well is, and that deserves its own attention.
The takeaway
A weekly long fast you can comfortably hold for months beats a punishing one you burn out on in six weeks. Pick your sweet-spot length, keep it to a rhythm with recovery built in, and rotate your protocol when things stall instead of just going harder. And watch for the one clear signal that you've overcooked it: a plateau that shows up at the same time you're feeling worn down. That's your body asking for a break, not for more.
~ Foster
By Foster
Questions people ask about this
I do a 45 to 48 hour fast every week and love it, but is that too much or unsustainable long-term?
A weekly 36 or 48, held for months with real recovery in between, is not too much for most healthy people. What is too much is grinding one hard protocol into the ground. I ran twenty-six straight 65-hour fasts once, and it eventually put me in conservation mode and on the floor.
Here is the tell that you have crossed the line. Fasting is a stressor, a good one but still a stressor, and the sign is not the fast itself, it is a stubborn plateau showing up at the same time you feel worn down by it. When those two arrive together, that is your body asking for a break, not for more. Sustainability is a rhythm with recovery built in, not the biggest number you can white-knuckle.
My fasting stopped working and I hit a plateau on the same protocol. What do I do?
Rotate the protocol instead of just going harder. When my alternate-day fasting stalled, I switched to 65-hour rolling fasts, and when those stalled, I switched back to alternate-day. Each time I broke through.
The key is to change one variable and keep everything else steady, same foods, same activity, just the fasting window, so you actually know what did the work. Rotating keeps your body from fully adapting and keeps the stress from compounding. Going longer and harder into a plateau usually just adds stress on top of a body that is already defending.
Am I undoing my weekly fast when I eat afterward?
Mostly, no. The bounce on the scale after you refeed is largely water weight, not fat you regained. Carbs pull water into your muscles, and one reading is only a moment in time.
Where it can actually work against you is if you come out of a long fast and overeat a system that has been resting. So the fast is rarely the hard part of a weekly rhythm. Coming out of it well is, and that deserves its own care.