Sheila Dillon finds out why the debate about the role of sugar in our lives is hotting up. Recent books and news stories have re-awoken a forty year debate about what makes us fat.Robert H. Lustig is a paediatric endocrinologist at the University of California, San Francisco. A lecture he gave on sugar has attracted more than three million hits. He makes a case that sugar is problematic, not just because it contains calories, but because the fructose component of sucrose interacts with our bodies in a very specific way. His claim that sugar not only causes obesity but a wide range of other conditions including type 2 diabetes, is disputed, but he's succeeded in capturing public attention. Sheila Dillon speaks to Robert Lustig about his research, and she explores other reasons why sugar is back in the headlines.