These two videos on obesity aren’t quite opposed, but they are interesting together. The first is Jeffrey Friedman’s presentation from last fall at Northwestern on leptin and genetics. The second is Robert Lustig’s recent presentation to the Harvard Food Law Society on sugar and metabolic syndrome.
Note: because Friedman’s presentation was to fellow docs and Lustig’s is to law students, the latter is definitely the more civilian-friendly of the two videos.
Jeffrey Friedman’s Biologic Basis of Obesity
Robert Lustig’s The Sugar Epidemic: Policy versus Politics
Weight Maven is written by Beth Mazur. Beth believes that obesity is more symptom than cause and that the real problem is our modern culture -- especially diet. Beth writes about ancestral health, health policy, & mindfulness. And cats! 
I have listened to both Friedman & Lustig. In fact, it was Lustig’s the Bitter Truth lecture that ignited my common sense and critical thinking skills and sent me in search of more information which lead me to paleo and weight loss. While leptin may have something to do with weight regulation, I’m not seeing how it ties in with the obesity epidemic.
Here’s how I look at leptin: it’s produced by our fat cells, and when it gets to a certain level, our bodies normally adjust by revving up our metabolism and slowing down our appetites. In Western culture, something is interfering with this mechanism. I think the biggest contributor is industrial food, but it could be other things like chemical pollutants or even epigenetics.