is Light Yagami anorexic in your opinion? ?

No, he's of an otherwise normal shape and size, in spite of a not-so-normal, oversized ego, scarred morals and a taste for blood. He actually gets a kick out of the pain and suffering of others, which all plays into feeding into his narcissism, egocentrism and utter self-centeredness.

That little human $#!t deserved to die.

He's been shown eating plenty of times, and he isn't emaciated, so he's definitely not anorexic. He hasn't been shown purging, so he's probably not bulimic, either.

L might have some sort of eating disorder, but it's not anorexia, either.

Nope. The guy deserver to die.

If I remember he eats a bag of chips and some snacks on a date in the first third of the show, but they've shown nothing that says he doesn't eat, so I'd say he's not anorexic. 

No, I don't think so. He looks in good shape.