Seeking Runner Input: Marathon, Fueling & Reta

[casprow]

Tomorrow I'm going to attempt a marathon as a personal challenge — never run one before. I began weekly reta injections at 2 mg 5 weeks back, so I'm curious how much this peptide will impact my distance running.

Any suggestions for decent, low-cost snacks or fuel mid-run that aren't gels?

Biggest thing I'm wondering: what timing do you use for dosing? Reta delays digestion, so if I eat a snack while running it'll linger in my stomach and take longer to kick in and give me the boost.

One more: heart rate — has anyone seen a change, either improved or worse runs, after starting reta?

 

[chode174]

For a marathon, I'd say you're probably okay. Since I run ultras, I learned the tough way that a month out from a race I have to quit Reta. The problem during a race was that my calorie burn got so high that food and drink simply couldn't get in fast enough, and I ended up with a DNF. That was a 100 miler, and I stopped at mile 70. Basically my body shut down, and it slipped my mind that Reta reduces how quickly your stomach processes intake. Because of Reta, I was burning calories way faster than I was absorbing them, and I hadn't accounted for that.

Training never made me think about it, so I never played with nutrition or hydration, but if you're going to race while using Reta, your training planning has to be different. These days I only take Reta for some weight loss, then I come off it and switch to CJC/Ipa, MOTSC, and KLOW. I'm thinking of running IGF-1 LR3 for a month for training, then moving over to HGH.

I've tested out the slower gastric intake from Reta, and it genuinely takes 4 weeks before it fully stops and goes back to baseline. I use psilocybin mushrooms as my gauge for whether my stomach has normalized. With about 2 grams of mushrooms, the feeling is different while on Reta. It's tough to put into words, but it's like the peak gets blocked from fully landing and instead just keeps stretching out. So I'll usually take the shrooms at the end of week 2 off Reta to check where I stand, then do it again at week 4.

Heart rate was never a problem for me. I've been doing long distance running for a while, and even when it raised my heart rate it didn't bother me, but after starting Reta my body would adapt to it in about 2-3 weeks and settle back to normal.

 

[onewalker]

I want to add my own experience to this topic and see if anyone can weigh in.

A bit of context first - my path looks a lot like what others have described here. I'm a 50M, and across roughly two years I dropped around 50 lbs, mostly thanks to Ozempic. Early this year I added Retatrutide (4 mg/week) plus Cagrilintide (1 mg/week), and I reached that dose on March 19 2026.

Running has been part of my life for about two years now. About a month ago I completed my first official half marathon, finishing in 2 hours and 8 minutes.

This morning I set out for what was supposed to be an easy 8 km or so. Right away something felt wrong, and before I even hit 2 km I had to quit running and switch to walking. When I checked my Apple Watch, my pulse was above 200! Stubborn as I am, I pushed through the whole 8+ km anyway, alternating walking and running. My pulse wouldn't settle though - it stayed racing, bouncing between 170 and 195 for the rest of the run.

Across the 100+ runs I've logged in the past two years, 178 was the highest heart rate I'd ever recorded, so this worries me quite a bit.

Things that came before the run and might explain the heart racing:

Last week I was travelling and went a full week without Reta/Cagri - then on Thursday I went back to my usual 4 mg/1 mg pin.

I drank some alcohol the night before - only a little, roughly a glass of wine plus a beer.

Late last night I spent probably two hours in a hot tub.

It was a hot day and I almost certainly didn't drink enough water.

Has anyone else dealt with intense heart racing while running on Reta?