How often do models eat?

I want to be a model for a part time job, but I'm afraid I might become anorexic or bulimic, because I know the modeling agencies are strict on eating and diets. They won't let you eat anything you want, and I get hungry and thirsty pretty face because I'm an anemic. I never understood why models couldn't eat just anything, because don't skinny people naturally have a fast metabolism anyway? The food would just pass through.