Robert H. Lustig, MD, Professor of Pediatrics in the Division of Endocrinology at the University of California, San Francisco, holds no punches during his lecture on "Sugar: The Bitter Truth." He takes a direct blow at sugar as the primary culprit for the obesity epidemic. The middle section on biochemistry is tedious, although it contains some pearls. If you want to jump through that section, pick back up at 1:08:29 on the time bar.
While he characterizes the Paleo foods as "raw" - not true of the Upper Paleolithic and maybe not since Homo erectus - he gets it right: the Paleo diet would prevent obesity and its many associated illness such as Type II diabetes.