Is the drug a long-term solution either, though? Won't the users regain the weight after stopping the drug, exactly like people who stop dieting do?

The trick with all lifestyle changes is to start as small as possible. Don't try to overhaul your eating and exercising habits overnight, but instead start from something small like "buy some fresh fruits every time you buy groceries" or "go outside for a bit every day whatever time you feel like it".