Robert Lustig is a paediatric endocrinologist at the University of California who specialises in the treatment of childhood obesity. A 90-minute talk he gave in 2009, titled Sugar: The Bitter Truth, has now been viewed more than six million times on YouTube. In it, Lustig argues forcefully that fructose, a form of sugar ubiquitous in modern diets, is a “poison” culpable for America’s obesity epide