I think Melissa share many of my reservations about the current theory of food-reward. Please read her article here.
I am going to edit my previous post to include that link, but if you were interested in my post about how modern food lies you might like her post as well.
Edited to add: Oh, look, Paul Jaminet seems to agree with me as well. Or, at any rate isn't quite on board with food-reward as it is currently advertised.
Though, let me take this moment to re-iterate that Stephan Guyenet is a very excellent blogger, seems to be a level-headed scientist, and also seems to be a nice guy. But I do believe that respectful disagreement is one great way to increase the total of knowledge.