Concerta is the same drug as Ritalin, I believe, and could well be the cause of your wakefulness and
loss of appetite. I take Adderall, a similar drug, to cope with fatigue, and it does dampen my hunger, for sure. It's a good consequence for me, if unintended. I take 20mg of the extended release type each morning, and can feel it wearing off by mid-afternoon. It doesn't affect my sleep.
It's possible your dosage is too high, so a consultation with your doctor is order.