I eat my boogers all the time, too. I'm pretty sure that since the boogers are excreted from your body, the caloric exchange is negligible. Think of it like this: You eat food, which your body uses to run all the systems of the body, including the production of boogers. You then take the booger and eat it. So, if you ate nothing but your own boogers, you would eventually starve to death.
Ergo, it's an excellent dieting plan.
Also, when you have a runny nose and then wait for it to dry up, those are the best boogers. It's like the almost crunchy, nice and sticky consistency. Mmmmm.
Incidentally, the same should hold true of any bodily production you consume. Fingernails, for example. But don't do that; it's DISGUSTING.
EDIT: Don't forget that your boogers exist to trap foreign bodies to prevent them from entering your lungs. Thus, when you eat your boogers, you may be ingesting bacteria that otherwise would never make it inside. Also, anything you can smell is a particle from the thing you're smelling. So if you pick your nose after you leave a smelly bathroom, you've just consumed tiny particles of someone else's pee/poop. Happy eating!