Water Fasting on GLPs: Thoughts?

C

Cluni0n

Explorer
Joined
Apr 26, 2026
Messages
20
Reaction score
0
Location
France
Like the title says, I’d like to hear what you think (and maybe what you’ve been through) about water fasting—meaning nothing but water plus electrolytes with 0 calories and 0 sugar—while taking GLPs such as retatrutide?

I’m not talking about intermittent fasting. I mean something more like 3 whole days, or perhaps a full week of water fasting. Would there be any upside to that, in your view? Does it justify doing it? Or is it simply pseudoscience?
 
There's a recent discussion about fasting


Has anyone here tried fasting while taking GLP1s?


I used to fast years back and enjoyed both the results and the mental sharpness it brought. I haven't done it in a long time, but I'm thinking about trying it again this weekend. Has anyone on here fasted while on a glp1? Because gastric emptying slows down, you'd need to be extra cautious about overeating once the fast is over.

051f0e2f5b7f6ffbb4a2f10b404546ba44b6197464dfbacec1b043fb189c69a3.png


GLP1Chat.com
 
I wrapped up a 3 day fast just yesterday. This was my initial attempt at fasting while taking GLPs, though I used to fast regularly several years back.

Staying hydrated was more of a challenge, but hunger didn't pull at my attention the way it once did. I experienced plenty of mental clarity and dropped a few pounds. Overall, it felt pretty much like my pre-med fasting days. I'll keep doing these going forward, since fasting has personally helped me when my autoimmune illness and/or allergies flare up.

The one issue I attribute to the glps was that refeeding felt worse. I had a small meal of my usual foods, and afterward my stomach stayed rumbly and unpleasantly full for a few hours.
 
Cluni0n said:

Like the title says, I’d like to hear what you think (and maybe what you’ve been through) about water fasting—meaning nothing but water plus electrolytes with 0 calories and 0 sugar—while taking GLPs such as retatrutide?

I’m not talking about intermittent fasting. I mean something more like 3 whole days, or perhaps a full week of water fasting. Would there be any upside to that, in your view? Does it justify doing it? Or is it simply pseudoscience?
Click to expand...
In my view, fasting brings a lot of benefits. Plenty of research examines caloric restriction in both animals and people. I won't get into the details here, but it's out there if you look. Combining GLPs with fasting has worked really well for me too. My longest water fast lasted 3 days, and I had no problems. I use an electrolyte powder that I mix up on my own — it's inexpensive and does the job well. If you search for "Snake Juice", you'll come across different versions of it. I increased the batch size, so I end up with roughly 2 cups of powder that I simply mix into a few liters of water over the course of the day.
 
Cluni0n said:

Like the title says, I’d like to hear what you think (and maybe what you’ve been through) about water fasting—meaning nothing but water plus electrolytes with 0 calories and 0 sugar—while taking GLPs such as retatrutide?

I’m not talking about intermittent fasting. I mean something more like 3 whole days, or perhaps a full week of water fasting. Would there be any upside to that, in your view? Does it justify doing it? Or is it simply pseudoscience?
Click to expand...
Occasional fasting appears to have some solid evidence behind it for organ health, the liver being one example. The idea with the liver is that it gets a rest period and can then turn its attention toward repair or something along those lines. A very large group of people are strong believers in this practice.
 
I tend to do long water fasts 1x/mo, roughly 3 to 5 days, as part of my keto & IF routines. Extended water fasting has genuine benefits and is definitely not pseudoscience. While fasting I add celtic salt to my water. I refeed with bone broth. I did a 5 day water fast at the end of June/early July, though that was during my off cycle bc I was getting my body ready for a procedure.

I haven't done a long water fast while on Reta bc I'm already eating less and haven't felt the need. It really comes down to how my gut feels and what I've been putting in my body. If my gut tells me it needs the fast, that's when I do it.
 
On Reta, after roughly 14 hours without eating, my fasting glucose in the morning came back at 55mg/dl — that was with a phlebotomist stopping by at 9am to draw the blood. Trying anything longer than that myself would scare me. I'm only bringing it up as something that could happen, so people know to watch for it.
 
Going without food for extended stretches does trigger genuine changes in the body. That said, when you combine several days of water-only fasting with a powerful agent like retatrutide, getting enough nutrients becomes a serious challenge.
 
I've been considering giving fasting a try. I've been taking reta for a while now. My appetite hasn't shrunk that much—I can still put away a decent amount of food. Before I started reta, I'd fast once or twice a year. Nothing extreme, maybe about a week doing an ADF-style pattern, eating every other day.

Honestly, the main driver is weight loss—I've put on around 10lbs since Jan. There are several factors behind that, but I feel like I need a reset. What worries me most is my blood sugar dropping because of the glp1. I'm hoping that won't be a problem.
 
Not for me — it seems risky. My blood sugar would likely fall too far. That's already a problem for me even when I eat on a normal schedule.

Back before GLPs, I used to fast for 24 to 36 hours to lose weight. It did work, but the headaches and exhaustion made it not worth it, and I couldn't keep it up.
 
If I don't feel hungry and occasionally go an entire day without eating, it's not a problem. Most of the time I already follow OMAD, or I'll have a shake in the mid-morning plus a meal afterward. Low blood sugar hasn't been an issue for me, and since I'm not particularly active during weekdays, those factors could explain why this approach has helped me drop 100+lbs.

But now that I'm smaller, simply cutting calories further isn't really an option since there's nothing left to cut, so I've started trying to eat more and move more. That's led to a frustrating two month stall, though I'll stick with it a few more weeks before abandoning it and heading off to find a desert where I can do a 40 day fast 😩
 
Drink plenty of fluids, and keep drinking. For every 12oz of water, add a small amount of sea salt along with a squeeze of lemon juice. Electrolytes that contain no calories…
 
At minimum, I aim for 1 fasting day each week. This was already part of my routine prior to starting glp-1, so it isn’t a new practice for me. Honestly, I haven’t noticed any major changes now that I’m on Reta. If anything, it feels slightly easier because of the reduced hunger... in my view, keeping hydration up is the most important part.
 
Back
Top