Everyone knows that American children are becoming fatter, but not everyone agrees on the cause. Many of today's children routinely consume more calories than they expend in physical activity, but this imbalance results from many recent changes in home, school, and neighborhood environments. Concerned about the health and economic costs of childhood obesity, in 2004 Congress asked the Centers for Disease Control and Prevention to examine one potential cause — the marketing of foods directly to children. The result is a new Institute of Medicine (IOM) study, Food Marketing to Children and Youth: Threat or Opportunity,1 that provides a chilling account of how this practice affects children's health. Food marketing, the IOM says, intentionally targets children who are too young to distinguish advertising from truth and induces them to eat high-calorie, low-nutrient (but highly profitable) "junk" foods; companies succeed so well in this effort that business-as-usual cannot be allowed to continue.