GLP-1 receptor agonists pharmacologically suppress colonic motility — and stimulant laxatives, the standard fix, create dependence without restoring function. Dr. Will Bulsiewicz explains what's actually happening and what effective treatment looks like.
If you're on a GLP-1 receptor agonist — whether semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound), or another in this class — you've probably experienced something that most diet plans don't warn you about: while you're finally losing weight, your digestive system feels like it's shut down.
You're not hungry. You can barely finish a small meal. And your bowels? They've gone quiet. Sometimes dangerously quiet.
This isn't a side effect you just tolerate. It's a physiological consequence that deserves understanding and a thoughtful solution.
I want to be clear: GLP-1s are remarkable medications. They work. The weight loss is real, and for many of my patients, it's transformative for their health. But the constipation? It's serious, it's common, and it's been treated with all the wrong solutions. Understanding why it happens is the first step to fixing it properly.
How GLP-1s Slow Your Gut
Let me walk through the physiology because it explains everything about why traditional laxatives fail for this specific problem.
GLP-1 is a hormone your intestines naturally produce when they detect nutrients — particularly glucose. It tells your pancreas to release insulin, slows gastric emptying (the rate at which your stomach releases food into your small intestine), and signals satiety to your brain. When you inject a GLP-1 receptor agonist, you're flooding your system with this hormone. Your stomach empties slowly. Your appetite suppresses dramatically. Your blood sugar steadies.
GLP-1 receptors are expressed throughout the GI tract, including on the smooth muscle cells of the colon. Activation of these receptors decreases colonic motility — coordinated peristaltic waves weaken, and the colon's intrinsic ability to move stool is pharmacologically suppressed.
Liu et al. (2025). Journal of the Science of Food and Agriculture, 105(15), 8664–8676. ↗
But here's what happens in your colon: GLP-1 receptors are expressed throughout your GI tract, including on the smooth muscle cells of your colon. Activation of these receptors decreases colonic motility. Your colon's muscle contractions slow. The coordinated peristaltic waves that normally propel stool forward weaken. You're not just eating less and therefore producing less stool (though that happens too). Your colon's intrinsic ability to move stool is pharmacologically suppressed.
Add to this the fact that you're eating significantly less volume overall, which means less physical distension of your colon — and distension is one of the natural stimuli for colonic contractions. You've got reduced stimulus and reduced muscular response. Your colon is a muscle, and like all muscles, it needs stimulus and use to function optimally. GLP-1s remove both.
Why Stimulant Laxatives Make It Worse
Here's where I see the biggest mistake. A patient on a GLP-1 develops constipation. Their doctor or nurse suggests senna or another stimulant laxative. The patient takes it, gets some relief, and then relies on it more and more frequently.
This is exactly the wrong solution for GLP-1-induced constipation.
Stimulant laxatives work by irritating the intestinal lining and forcing muscle contractions. But if your gut motility is already pharmacologically suppressed by the GLP-1, adding a stimulant creates a dysrhythmic, chaotic pattern. Your colon gets artificially stimulated to contract, but it's not actually recovering its normal rhythm. You become dependent. And worse, you're adding irritation to an already-struggling system.
What you need isn't more irritation. You need restoration of actual motility, combined with the other factors that make stool move: proper stool consistency, adequate bacterial signaling, and microbiota support. Stimulant laxatives address none of these.
Introducing RCE™: Root-Cause Regularity
38TERA® is launching RCE™ in May, and this product is built specifically for the GLP-1 population because it addresses what GLP-1s actually break.
RCE™ works through three complementary mechanisms:
First: Gut Motility and Rhythm Support.
Unlike stimulant laxatives that force artificial contractions, RCE™ contains ingredients that support your colon's intrinsic contractile function. It restores the neural signaling and smooth muscle tone that GLP-1s suppress. You're not forcing your gut to move; you're restoring its ability to move on its own. This is why it works with GLP-1 therapy rather than fighting against it.
Second: Stool Softening.
GLP-1s reduce the volume of food and water entering your colon, which paradoxically makes stool harder, not softer. Your colon reabsorbs more water from what little stool you produce. RCE™ gently increases water content and softens stool, making it easier to pass without the harsh irritation of senna-based products. It works osmotically but with additional factors that support healthy stool formation.
Third: Gut Microbiome Nourishment.
This is the piece most constipation products completely ignore. Your gut bacteria produce short-chain fatty acids that signal your colonic nerves and muscles to contract. When you're on a GLP-1 eating significantly less food, your microbiota is starving. RCE™ includes prebiotic fiber and a heat-treated postbiotic (Plenibiotic™) that directly nourishes and supports beneficial bacterial species like Bifidobacterium. It's not just about feeding bacteria; it's about feeding the right bacteria — the ones that support motility.
You're not forcing your gut to move. You're restoring its ability to move on its own.
| Problem with GLP-1 Constipation | What Stimulant Laxatives Do | What RCE™ Does Instead |
|---|---|---|
| Suppressed colonic motility | Force unnatural contractions; create dependence | Restore intrinsic motility and neural signaling |
| Hard, dry stool from reduced intake | Add irritation and water loss | Gently hydrate stool and support normal passage |
| Starving, dysbiotic microbiota | Nothing — ignore the microbiota entirely | Nourish beneficial bacteria; restore SCFA production |
| Loss of normal rhythm | Replace rhythm with artificial stimulation | Rebuild the body's own rhythmic capacity |
The Philosophy Behind RCE™
Here's what separates 38TERA®'s approach from legacy constipation products: we're not chasing quick fixes. We're targeting root causes.
When you take RCE™, you're not just getting immediate relief (though you will). You're supporting the restoration of your gut's native capacity to move stool. You're feeding your microbiota back to health. You're working with your GLP-1 therapy, not against it.
This matters because many patients on GLP-1s reach a point where they want to reduce their dose or eventually discontinue. If you've spent months relying on stimulant laxatives, your colon is even weaker than it was when you started — you've created iatrogenic (drug-induced) dependence. But if you've used RCE™ — supporting motility, nourishing your microbiota, maintaining stool quality — your gut maintains its capacity. When you eventually adjust your GLP-1 dose, your colon remembers how to work.
This is built from my clinical experience. I've treated tens of thousands of patients. I've watched what works and what creates more problems. I've built a bestselling course on constipation precisely because this condition deserves this level of depth.
Your Next Step
If you're on a GLP-1 and experiencing constipation, talk to your prescribing doctor about RCE™. Come May 2026, it will be available at 38TERA®. This isn't a product designed by committee; it's designed by a gastroenterologist who understands what you're going through because I've stood across from thousands of patients in your exact situation.
Your weight loss journey doesn't have to come with digestive suffering. There's a better way.
Key Takeaways
- GLP-1 receptor agonists suppress colonic motility directly — via receptors on smooth muscle cells — while also reducing the food volume that naturally stimulates contractions.
- Stimulant laxatives are the wrong solution: they create dysrhythmic contractions and dependence without restoring the gut's native ability to move.
- Effective treatment for GLP-1-induced constipation requires three things together: motility restoration, stool hydration, and microbiota nourishment.
- RCE™ is built specifically to work with GLP-1 therapy — not against it — by targeting root causes rather than forcing a short-term outcome.
- Patients who rely on stimulant laxatives through GLP-1 therapy risk iatrogenic dependence. Supporting gut function properly preserves colonic capacity when dose is adjusted or discontinued.
References
- Liu, K., Zhang, Y., Cai, H., Song, S., Ai, C., & Yang, J. (2025). Ulva lactuca polysaccharides alleviate constipation in mice through repairing the intestinal barrier and regulating the gut microbiota. Journal of the Science of Food and Agriculture, 105(15), 8664–8676. https://doi.org/10.1002/jsfa.70108
- Tekulapally, K.R., Lee, J.Y., Kim, D.S., Rahman, M.M., Park, C.K., & Kim, Y.H. (2024). Dual role of transient receptor potential ankyrin 1 in respiratory and gastrointestinal physiology: From molecular mechanisms to therapeutic targets. Frontiers in Physiology, 15, 1413902. https://doi.org/10.3389/fphys.2024.1413902
Leave a comment
This site is protected by hCaptcha and the hCaptcha Privacy Policy and Terms of Service apply.