Never heard that (aint as big as a fanatic as some of you guys seem to be, only seen about 7 episodes doh!). But to respond to geo81:

I came to figure that Dave always appears whenever Hurley is tempted to food, or is around it nevertheless. Dave is just a part of Hurley's subconcience to keep Hurley where his is happy. Hurley always seems to be in a positive mood when he is eating, and his body reconizes this and uses this as leverage to keep Hurley happy. His mind creates a friend or of someone Hurley wants to be (kind of like in fight club) inorder to keep peace. Dave shows up when Hurley is depressed but it near food, in an attempt to save Hurley. And when Hurley's mind realises that Hurley is giving up to the temptation, a desperate act to save the mind (somehow) is to kill Hurley.