Sudden increase in appetite

For the past few days I've been really hungry, all the time. I'll eat more food than I usually would and still feel hungry. I feel like I could eat an obscene amount of food. I'm not pregnant. I've been on a diet but I'm definitely not depriving myself, I've been on this diet for months and not had this problem, and I've also never felt this hungry just from being on a diet. Any ideas for what could be causing this?