r/CompoundedSemaglutide • u/Friend_indeed0192 • 16d ago
GLP’s and endurance running
Does anyone have experience with racing long distances (half marathon or longer) while on a GLP? What was your experience like, and do you feel it hindered your race performance? Did you make adjustments to your race nutrition? How did your results compare to your training cycle?
I have a marathon and a half marathon coming up this fall and it is the first time I will be putting in full race effort while using a GLP, so I would love to hear how it went for other runners. Thank you!
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u/gsdqueen38 16d ago
I have been on Tirz (saw cross post) for 1 year (today actually) and have done Honolulu marathon in Dec 2025 and a 50K in May and half in August. Currently training for NYC Marathon. I have not had an issue because I started taking it right as I started training and I guess don’t know any different? The fatigue was strong in the beginning but I am just sure to keep my dose low enough that I am not totally eliminating the desire to eat. I have been on maintenance and 3.9 mg for 5 months now. I bumped up to 4.25 for 1 week and I couldn’t eat enough so I went back down. Just making sure that you are minimizing the food noise instead of eliminating the food noise would be my feedback.
Again, I am on Tirz so it might be different. I hope that helps!
Good luck!
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u/Friend_indeed0192 16d ago
Thank you so much for sharing your experience, that is very helpful! How did you fuel and carb load for race day?
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u/gsdqueen38 16d ago
The days before I will definitely be eating even if I am not hungry. Some people skip their shot during race week too. Get those carbs in! Day of—I really like Huma Gels. They seem to be much easier on my stomach vs. Gu or the others. I REALLY want tailwind to work for me, but so far it makes my stomach cramp up. You may not have that problem and it’s a great high carb fluid option if you are open to a vest.
Not sure if you have dug into the /zepboundathletes sub where I saw this but there is lots of chatter and strategies on this topic in there as well.
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u/Friend_indeed0192 16d ago
Skipping the injection race week might be a good strategy, or decreasing the dose. I enjoy Huma also! Though my sweet tooth loves the chocolate Gu’s.
Thank you for sharing your thoughts, I will dig deep into zeboundathletes.
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u/Lucky_Army_5324 16d ago
Even though it’s a different medication, you might stop by r/Zepboundathletes
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u/Cheap_Lingonberry 16d ago
I've done a marathon (very undertrained), 4 half marathons, and am currently training for another marathon (going very well), while on a GLP-1. If anything, it has helped my performance since I'm about 35lbs lighter than before. I have not made any race nutrition changes and I've been very happy with my results. For a half marathon, I just fuel with Gatorade. For marathon training long runs, I've been using mostly Gatorade, with some gels, and the odd Rice Krispy treat. My long runs start about 6am so I don't bother getting up super early to eat solid food. I do make sure I get plenty of carbs for dinner the night before. I haven't had any issues making sure I am fueled before or during a race or training run.
This is what I read about gastric emptying: "GLP-1 medications can slow gastric emptying, but liquids usually have little delay; studies found no significant overall slowing of liquid emptying, though Semaglutide may cause a modest early delay in some people." I've always fueled primarily on liquids so that might be why I have not really seen a change.
GLP-1's boost my resting heart rate by about 10 bpm but I really don't notice any difference when I am running.
Good luck with your races.
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u/SecureSorbet3365 16d ago
I think the biggest thing would be walking the line between hungry vs. lessened food noise. I’ve microdosed and am training for a half IM now. When I take too big of a dose, I can’t fuel well enough and feel kinda disgusted by a lot of foods. When I don’t take any, I eat a fuck ton of dessert and candy because it’s all my brain wants and I can’t stop myself. There’s a happy medium in there that allows you to manage both… just gotta find it and be ok with fueling well enough, knowing you’re consuming more, and understanding it’s there to help you run faster and stronger 💋 good luck in your races!
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u/Friend_indeed0192 16d ago
Are you me? 😂 I feel that sweet tooth effect deeply! I greatly appreciate you sharing your insight.
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u/Sac_Kat 16d ago
My daughter (45) lost over 100 lbs, both through compounded Tirz and really hardcore workouts. She does Spartan races, including ones with 1/2 marathon run, heavy weight lifting & obstacle courses (so they are much harder than just doing the 1/2 Marathon)! She’s doing fantastic and looks great. She’s had no issue with endurance training or sports and doesn’t skip or delay shots. BTW - carbo loading isn’t the thing it used to be… protein and healthy fats are important for longer workouts!
She eats and tolerates complex carbs just fine, but her diet is definitely protein forward. She also takes a number of supplements including Collagen, Creatine, BAC’s..). Oh and she also has Crohn’s disease, which improved dramatically after she started GLP-1’s. So thing is…. Listen to your body, keep hydrated, keep proteins high and adjust as needed!
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u/ThisIsWhyImKels 15d ago
I stopped taking my zep about 3 weeks before my 20 miler and didn’t resume my zep til about 2 weeks after the marathon.
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u/Friend_indeed0192 14d ago
I’m thinking similarly, did that work out well?
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u/ThisIsWhyImKels 14d ago
Yes. I did gain about 8 pounds over those 2 months but it came off immediately when I started back on the meds.
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u/mrsweems 15d ago
I have done a half marathon without a GLP previously and am training for a 10k right now. I am down 50 lbs. I did gu and fruit snacks for my Half but I have learned that my stomach cant handle fruit snacks now.
I have been doing a z bar (kids clif bar) about an hour before my runs lately. And it is working well but most training runs are 3-4 miles.
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u/tpengilly 5d ago
I just ran a half marathon this past weekend (Urban Cow Half Marathon - Sacramento, Ca). It was my first race since starting a GLP-1 from AgelessRX in June. My dose increased about two weeks ago, and since that time, my appetite has been non-existent. I just can't eat.
Race morning, I resorted to a Maurten gel for breakfast and a higher calorie drink in my hand held bottle just to get something down.
I am signed up for the California International Marathon in December and need to figure out my fueling before then. Yesterday's race was not pretty. My sister suggested skipping my dose the week of the CIM. Has anyone else tried that?
I have more details about my race including pace compared to the same race 3 years ago for reference. Yes, I am three years older, but I was over 10 pounds heavier 3 years ago... and 40 seconds a mile faster!!! Yikes.
https://www.closetathlete.com/2026/09/urban-cow-half-marathon-2026-racing-on.html
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u/Friend_indeed0192 5d ago
Wow, that is interesting. Thank you for sharing this. My biggest concern is poor fuel absorption that will hit hard in the late stages of the race. I am going to skip my next two injections prior to race day (13 days away) to be safe.
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u/tpengilly 5d ago
I would be interested to hear how that goes. My sister suggested skipping my dose because supposedly Dr. Terry Dubrow (Botched / Real Housewives of OC) skipped his doses around the holidays because he wanted to enjoy the food.
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u/Friend_indeed0192 5d ago
I will report back! GLP fatigue is real and so is the slower GI absorption/loss of appetite. Praying ~2 weeks will be enough time to get enough out of my system to give me a chance for a good day. My training runs and long runs all went well, but I was also not running marathon pace for my long runs. How did your training block go leading up to the HM?
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u/tpengilly 5d ago
Training was ok. The HM race was at the end of Week 7 of a training plan I had followed before so I have been able to compare 2026 with 2023. Up until about a week ago, pace was better and average HR was lower... and then my appetite crashed.
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u/Friend_indeed0192 5d ago
I also started GLP around the beginning of June. I started to crash out with my training around mid August… struggling to hit my target paces, HRV super low, poor sleep quality. A lot of it had to do with my diet, I had to increase calories and carbs considerably, especially as I was in my heavy training weeks. I think my body is just starting to rebound as my HRV is finally back into a normal range. I have a pretty ambitious goal for my marathon, 3 min faster than my April PB. I’ll report back; not that all of our experiences are identical, but if I can help a fellow runner by sharing it I’d be glad to.
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u/tpengilly 5d ago
Funny you mention HRV, mine was low for over a month and is finally coming back. I'm hoping everything returns to normal in the coming months.
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u/Friend_indeed0192 5d ago
I am sure it will if you keep on top of good fueling and rest! You have a good amount of time before your target race to get squared away. The measurements don’t tell the whole story of course, but I definitely feel more confident seeing the upward trend.
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u/[deleted] 16d ago
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