Orthorexia Nervosa

Orthorexia Nervosa is an eating disorder defined by an escalating obsession with eating "healthfully."

http://en.wikipedia.org/wiki/Orthorexia

The term was coined by Dr. Stephen Bratman, who identified a fixation on a diet that can be perceived as morally pure. "Where the bulimic and anorexic focus on the quantity of food, the orthorexic fixates on its quality."

Here's his original article on the subject, called Health Food Junkies. It's insanely interesting.

http://www.beyondveg.com/bratman-s/hfj/hf-junkie-1a.shtml