Dr Robert Lustig is a pediatric endocrinologist at UC San Francisco, and has become well known for his 2009 YouTube video, Sugar: The Bitter Truth. This video has over 7 million views as of April 2017.

Here he is interviewed by CrossFit’s Rory McKernan to explain sugar’s toxicity, and how processed food—often loaded with refined carbohydrates and added sugar—is a huge part of the obesity and diabetes problem.