I can't remember the technical terms for these issues (hypercaloric, nutrient deficient diets or something) but I watch a documentary covering malnutrition. They showed people eating cheap food with low nutrient dense foods because they were ignorant and/or poor. Another documentary, Vitamania (great watch), showed that we only need a small portion of nutrients compared to the volume of food we eat. So, I imagine it's more about health education and financial status than people "eating right" while over estimating their nutrient intake.