Hungry days

I am having a really really hungry day today. It doesn't matter how much I eat fruit or salad or veg etc I just don't fill the gaping hole I seem to have! None of it feels satisfying. I'm not craving specific foods, just feel like I NEED to eat! I feel starving! On other days I don't mind the slight hungry feeling, even find it comforting because it means I'm in control but it's not slight hunger today, or the last few days actually.
Does anyone else get this? How do you cope with those empty/hungry days?