Interesting. Something that immediately springs to mind is the potential evolutionary aspect that wasn't mentioned. Refined foods would provide more energy and suppress the hormones (stress hormones) that would make one active in order to search out more food. Being well fed doesn't exactly motivate one to expend excessive amounts of energy. In this context exercise is a surrogate activity replacing the search for food. But yeah in generally I believe that Nutrient density of food matters to a degree. The problem is in finding these foods. Even the refined foods would be higher in them if better farming and agricultural practises were followed.