The latest biological, sociological, and anthropological understandings of obesity all point to the idea that its far more complex than an unbalanced caloric intake. Here's the NYTimes take, reporting on a new study in JAMA: it's more about quality of food rather than quantity, and the increasing amounts of simple carbohydrates in our diets are changing the way our natural metabolisms function, in effect pushing up natural weight "set points." Take home message: don't necessarily eat less, just eat better (more veggies, less refined carbohydrates).
If this hypothesis turns out to be correct, it will have immediate implications for public health. It would mean that the decades-long focus on calorie restriction was destined to fail for most people. Information about calorie content would remain relevant, not as a strategy for weight loss, but rather to help people avoid eating too much highly processed food loaded with rapidly digesting carbohydrates. But obesity treatment would more appropriately focus on diet quality rather than calorie quantity.