It is different for everyone, and that is not a dodge, it is the real answer. Here is a more useful way to think about it.
In the first week or two
Many people notice appetite changes before anything shows up on a scale. Smaller portions feel like enough. Food takes up less mental space. Some people feel it after the very first dose. Others take a couple of weeks to notice anything at all.
Your first weeks are a starting dose, not a working dose
Everyone starts low. That is on purpose. It gives your body time to adjust and keeps side effects down. Your provider steps the dose up over time, and changes often become clearer as that happens.
Progress is not a straight line
Flat weeks happen. They do not mean it stopped working. Keep going!
What matters alongside the medicine
Eating enough protein. Some form of strength training. Real sleep. Staying hydrated. The medicine makes eating less feel possible. The habits are what make it last.
If weeks go by and you notice nothing at all — no appetite change, nothing — tell your provider. That is useful information, not a complaint.