I'm an Adderall addict and quite a bit chubby myself, the thing about prescription amphetamine abuse is that the controlled dispensation and clearly defined dosage doesn't lend itself to the same kind of acute damage you see in full blown tweakers. It's more of a chronic disease and in order to remain as functioning addicts we do regularly come down to get food and sleep.

The difference is a street user can blow through a gram and go buy another one as long as they've got the cash whereas a prescription abuser is discouraged from recklessly binging because A. It's plain to see when you're going overboard (Once you're popping 4-5 in a day you realize you're losing the mental faculty to even keep track of how many you've taken) and B. even if you've got a loose doctor they're still gonna realize what's going on and not let it get out of hand.

I bet Trump's on even more than that though, with a comedown cocktail in the evening and that probably explains all the extra helpings at dinner; Not much to eat during the day except soda so by the time the Xanax/whatever kicks in his blood sugar's tanked so he's fucking starving and he scarfs down enough food to get him through the next day.