Why Is It...

Why is it that for so long I can live not knowing what it is I want to eat, so although I have cupboards and a refrigerator full of food, I find nothing I want and don't eat, but the moment I deny myself certain types of food (i.e. junk, sugar, carbs, fatty, etc) its all I can think about? Those foods that I am allowing (i.e. fruit, veggies, and lots and lots of salad) don't interest me at all, and only seem to make me hungrier. I have discovered that Slim Fast is actually really tasty and does work to fiend off hunger for the 4 hours it promises, so that's good, but this "diet" is going to kill me.