Unfortunately, so far there is zero scientific research on this subject. I would suggest go straight to reta, if the response is poor to glp-1 agonists it might not be to it plus gip and glucagon, or cagri or eloralintide as they work on a entirely separate system , amylin. There are genetic variants on the GLP-1 receptor itself and in the downstream signalling pathways that can be a cause for a poor response to GLP drugs, and this is probably the reason why 5-10% of people lose little or no weight on them. Eventually there will be studies done regarding what to do if this happens, but nothing yet. I would say the odds of a poor response to tirz or reta are fairly high, definitely worse than average, but no good data to go on. But they are amazing drugs for most people and it is worth spending a month or 2 or 3 trying out reta to see if it seems to work. And if not then try cagri or eloralintide.
I cannot say I lost any weight on ozempic, being on low doses for a year, it made me tired and feel a bit ill and a bit nauseated the whole time, but it did reduce appetite a bit to make it a bit easier to maintain a 70 kg weight loss. Thankfully 15mg of tirz plus 5mg of reta plus 0.5mg of cagri had much better appetite suppression and less nausea than 0.8mg/week of ozempic, and I lost another 14 kg or so on it over the next year
