Why do American's have such a big appetite for big food? It seems like everywhere you turn nowadays, there's a fast food restaurant offering a new double-bacon-cheese-filled item that you can wash down with a large fries, and a 32-ounce soft drink. We speak to Dr. David Kessler, author of The End of Overeating: Taking Control of the Insatiable American Appetite, about why he says we've become a nation of "conditioned hypereaters."