I was on phentermine for weight loss before switching to semaglutide. I found the former would suppress my appetite well for several months, and then the effect vanished as tolerance built. If the parent commenter is finding that amphetamines work indefinitely for appetite suppression, great, but they often do not.
For ADHD people, some of the weight loss from Adderal comes from reduced ADHD symptoms, like reduced dopamine seeking, so you stop mindlessly eating whole bags of chips, and reduced self medication with other drugs like weed and alcohol
You will also get these effects with caffeine and cocaine.