Have you looked at other similar medications? I'm on Vyvanse, which is very similar except that it only comes in a time-release form. Adderall has a time-release version, but you may not be on that. If it seems to wear off after 4-6 hours, you're not on the time-release version.

I find that i feel the effects of my Vyvanse nearly all day, and it's only for the last few hours of the night that it fades. So though I do have to be a bit careful then to similarly restrict eating, if I can trick myself by like, brushing my teeth early or drinking a lot of water before it wears off, that can help with (though obviously not cure) the binge eating.