I don't mean to derail your discussion, but I came across this video a couple of days ago:
Sugar: The Bitter Truthhttp://www.youtube.com/watch?v=dBnniua6-oM
Robert H. Lustig, MD, UCSF Professor of Pediatrics in the Division of Endocrinology, explores the damage caused by sugary foods. He argues that fructose (too much) and fiber (not enough) appear to be cornerstones of the obesity epidemic through their effects on insulin.
It's a long one, but I definitely thought it was very interesting and very convincing. Since your discussion involves the cause of obesity, I thought I'd just throw this out there. I'd be interested to hear your opinions on this.