This brilliant talk by Dr. Robert Lustig persuasively argues that sugar, based on how our bodies metabolize it in the liver, is no less a poison than alcohol. He explains how our bodies process different carbohydrates like glucose, sucrose (table sugar), and fructose, and why sugar in the latter two forms is the primary cause of obesity, high blood pressure, heart disease, diabetes, and more. He also debunks many common myths of health and nutrition by showing that a calorie is not a calorie (its source is important), why exercising is not about burning calories but improving metabolism, why fat is nowhere near as bad as sugar, etc. Also read this review of the related new documentary, Fed Up.