Water is an essential when taking adderall/dexedrine. It's a diuretic (flushes water out) and dehydrates. It's a possibility that your hunger is actually from lack of hydration and you need to drink OVER the recommended 8 glasses a day. Water - not pop or coffee as they are also diuretics.
Losing weight with adderall is always short-lived anyway. That's why it got stopped for being Rx'ed as a diet pill. You have to take more and more until you get sick. Not a good thing. I find that any changes in diet go away after a month or two. I lost weight for about 2 months then now I am level and don't over or under eat.
If you find during the day the usual lack of appetite - try setting up a timetable where you nibble on small meals - 3 to 6 of things like carrot sticks, crackers and other finger foods. Try to make them flavorful and small then you don't feel like it's a chore.
If it becomes a real worry for you - ask your MD. When it comes down to it they have more info at hand than we do. And there are ways to bring appetite back to normal if needed.