GLP isn't an appetite suppressant. It's a naturally produced hormone that's central to the energy homeostasis (weight regulation) system.
Tolerance doesn't develop to insulin, or testosterone, requiring ever increasing doses.
All the evidence shows at a fixed dose, weight drops to a certain level, and stays there, with some minor variation, until the dose is titrated up, then weight drops more, and stays there until it's titrated up again.
Once treatment is stoped, in the overwhelming majority of cases, weight gradually returns.
If tolerance developed, then weight wouldn't stabilize for years at the same dose, but gradually return as tolerance builds. A "maintainance dose" wouldn't be possible, yet it clearly exists.
When people get bariatric surgery, weight loss and improved glucose control aren't because their stomachs are reduced in size, but because food moves into the intestines quickly, stretching them more than usual. Intestinal hypertrophy releases GLP-1, and this increased level of GLP has all the same effects as a shot of the exogenous GLP.
Basically, this is the *hard way* of compensating for a GLP hormone deficit vs injecting it.
Two of the most popular bariatric procedures, vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB), are commonly considered metabolic surgeries because they are thought to affect metabolism in a weight loss–independent manner. In ...
pmc.ncbi.nlm.nih.gov
If someone stays on the same dose of exogenous GLPs, and weight starts to return, that's a sign of immunogenicity, with antibodies developing to neutralize the drug. Immunogenicity didn't rise to a clinically significant level in the pharma trials of Sema and Tirz (it has with other pharma GLPs), but we're not dealing with carefully manufactured pharma products designed to minimize that reaction. It's entirely possible haphazard use of UGL versions are gradually making people immune to Sema and Tirz, reducing or completely eliminating their effectiveness.