The reason I posted that article is because it summarizes how there has been a huge shift in thinking since the low-fat craze. I don't think it takes anything for granted, and I wasn't looking to argue for a particular point of view. I'm sure you can find studies about a specific topic as easily as I can.

Re caloric density: it's true that fat has more cal/g than carbs or protein. But, people do not eat a fixed mass of food per day -- the satiety of the food they consume influences this. Insulin response also affects weight gain and satiety.