I get hungry but I don't feel like eating?

Basically, since I've gone away to school, I've been eating much less than I did at home. I get hungry, don't get me wrong - I just don't feel like eating anything, like it feels almost pointless because I have no interest in food. I eat an average of 800 calories a day, though today I had much less. I know this is related to my loneliness here. How can I make my appetite reappear?