Gary Taubes, author of Good Calories, Bad Calories, talks to EconTalk host Russ Roberts about what we know about the relationship between diet and disease. Taubes argues that for decades, doctors, the medical establishment, and government agencies encouraged Americans to reduce fat in their diet and increase carbohydrates in order to reduce heart disease. Taubes argues that the evidence for the connection between fat in the diet and heart disease was weak yet the consensus in favor of low-fat diets remained strong. Casual evidence (such as low heart disease rates among populations with little fat in their diet) ignores the possibilities that other factors such as low sugar consumption may explain the relationship. Underlying the conversation is a theme that causation can be difficult to establish in complex systems such as the human body and the economy.