Not less nutritious food? Or is the argument that the [everything else] to calorie ratio should be higher?
Yep, that.
My understanding of this argument (which for the record, I'm loosely convinced is probably true, but probably isn't the only, and maybe not the main, factor) is that your body's hungry signal is it needs non-calorie nutrients, but our food is less nutrient dense so you get a lot more calories than your body is prepared to handle for a given quantity of nutrients.