Is sugar a toxin that's fueling the global obesity epidemic? That's the argument UCSF's Dr. Robert Lustig made in "Sugar: The Bitter Truth," a 2009 UCTV video that's since gone viral and sparked a national dialogue. In "The Skinny on Obesity," a 7-part series from UCTV Prime, Dr. Lustig and two of his UCSF colleagues tease out the science behind this alarming claim and the dire threat it poses to global public health.