I did this in the other direction. (I do not have diabetes -- just losing some weight I had gained back after bariatric surgery 15 years ago.) I lost weight on tirzepatide, struggled with the side effects, and shifted to semaglutide for maintenance. I have a history of weight cycling (which means I've gained and lost and gained and lost weight over much of my life), so I knew when I got on this ride, I would need to stay on it for life.

I would say that switching is a great choice, because people who have problems with one formulation don't necessarily have the same problems with the other. Also, not surprisingly, there is not a lot of research on this topic, because really, who would pay for it? This is a bit old, but the most helpful paper I found: https://pmc.ncbi.nlm.nih.gov/articles/PMC7900946/.

Yes, titration is critical if you are prone to side effects, and weight loss is unlikely at the initial low dose. I titrated up on the tirzepatide even more slowly than recommended, and held below the max dose until I lost most of my goal weight, because my side effects were pretty awful. Nonetheless, the tirzepatide got me there. I then titrated down before switching to semaglutide, and titrated back up a little bit for a maintenance dose.

Yes, it's really common for the weight to come back on when you stop, because the drugs do nothing structural, don't retrain us, and leave the body relatively fast. There are pretty deep arguments going on in the field between the on-it-for-life-this-is-equivalent-to-a-statin camp, and the make-lifestyle-modifications-and-then-stop-the-drug-and-it-will-all-be-fine camp. The problem is that insurance doesn't want to pay for the drug for life, and they also don't want to pay to support all the work needed for the lifestyle changes. It's a disease, and willpower doesn't work to conquer a disease, so the lifestyle changes are not trivial. As you can tell, I'm in the first camp. (As a result, I continue to keep an eye out for new formulations and options.)

Unfortunately, you can't click-count or microdose with the single-dose pens that Mounjaro and Zepbound use, which could otherwise be helpful in managing side effects and price.

Also unfortunately, the maintenance dose that is now managing most of my side effects pretty effectively, also brought back the "food noise". So far, I've been managing through that problem.

If you have not considered it, you might talk with your doctor about bariatric surgery. Surgery always comes with risk, of course, but I found it amazing and only wish I had been ready to consider it when I was younger. The weight regain was very slow and honestly, in part my own fault for not maintaining the behavioral changes. Unlike the drugs, where they just throw you in the deep end and walk away, the surgery should come along with comprehensive support for behavioral/lifestyle changes. And there is something to be said for one-and-done. I have no idea if insurance would require you to demonstrate weight gain after coming off the drugs before they would approve the surgery -- mine happened before the drugs were an option.