I'm not going to immediately jump onto the "You're starving yourself!" train. Because it really depends on how much you're still eating. A lot of people -- myself included -- will munch on things out of habit or boredom, not because we're hungry/in need of fuel.

So, as long as you're still eating, probably, between 1,200 and 2,000 calories a day, it's really not a big deal (though, it would be good to get some exercise, too). But, as others have said, if you're skipping real meals/snacks for WoW...yeah, that's not good.