read Good Calories, Bad Calories for a well researched book on why this is (http://www.amazon.com/Good-Calories-Bad-Controversial-Scienc...)
Taubes says that the current U.S. obesity epidemic actually consists of a very small increase in the average body mass index.
Interesting, considering the data in the top link implies otherwise. (I haven't read the book, can't comment on the editorial review's statement's accuracy)