I take it semi-literally to be intended to mean "Look at this!!! It's so good for someone else that you'll never be able to love or even find enjoyment in anything else again!!! Nyahh Nyahhh Pbbbbbbtttttttt." I have no historical facts to back up my logical assessment...making it pure speculation and only worth $0.02... but it's my $0.02.

LOL. I've seen that line in an Archie comic. I don't know if that's where it originated. I do think it is quite a weird thing to say. :)

Here's what I found: "Heart is also defined as the central, core, or inner most part of an object (or person). To eat the heart out is to remove the core or most important part, a part that will surely be missed. The phrase is probably a shortened way of saying "This will eat your heart out". Alternatively, Adapted from the 16th century "eat one's own heart", meaning to suffer from silent grief or vexation. It also has roots in the Biblical phrase, "to eat one’s own flesh", used to describe an indolent person." http://members.aol.com/MorelandC/HaveOriginsData.htm So basically when someone says that to you, they're saying that whatever they're talking about will destroy you.

"eat one's (own) heart: suffer from silent grief or vexation." Further down the page, "c. To destroy as a parasite or a corrosive. Also fig., esp. in phrases with heart... 1890 Review of Reviews II. 323/1 General Boulanger is not eating out his heart in vain regrets. 1919 M. K. BRADBY Psychoanalysis 70 Commonsense says that it is better..'to let off steam' than to 'eat your heart out'." http://www.phrases.org.uk/bulletin_board/45/messages/1112.html "...The ancient Greeks had an expression (quoted by Plutarch as a 'Parable of Pythagoras') that translates as 'Eat not the heart.' It meant not to consume oneself with troubles or worries, which could be almost as devastating as eating one's heart." "Dictionary of Cliches" by James Rogers (Wings Books, Originally New York: Facts on File Publications, 1985). http://www.phrases.org.uk/bulletin_board/46/messages/99.html eat one's heart out Feel bitter anguish, grief, worry, jealousy, or another strong negative emotion. For example, She is still eating her heart out over being fired, or Eat your heart out--my new car is being delivered today. This hyperbolic expression alludes to strong feelings gnawing at one's heart. [Late 1500s] http://www.answers.com/eat+your+heart+out?cat=biz-fin Variations: "eat your heart out", "play your heart out" and "sing your heart out".