For me I get so hungry when I get hungry. I need to eat right then. If I don't then I get dizzy and I feel sick. But if I wait too long to eat then I can't eat anymore. Food looks and tastes gross.
Stress can get you to not eat. I had it for about a week, but I got over it with some antacid. While I had it I felt like shit in every way, but only during the day the last 3 days for some odd reason. Before I would occasionally get numb to hunger then consume like a black hole the likes of which no astronomer has ever seen. My friends thought it was amazing that I could eat 2 footlong coneys if I didn't eat since breakfast.