The way the foods are now processed has changed. Foods used to have real ingredients not the much cheaper highly refined ingredients used today.
Still --- my kids go to the same kinds of schools mentioned in the article --- they're served the same fattening "ethnic" foods (politically correct meals), they play their share of video games --- but they aren't obese --- nor are the more active Mexican kids. What you run across in this area --- the food being consumed is the same for everyone --- the guys out baling hay aren't obese but the housing project dwellers almost all are. Everyone eats the fat and carbohydrate laded tamales and burritos --- but not everyone is fat. Some people replace the lard with small amounts of vegetable oil --- which kills the flavor but they seem to be slimmer. To me that's like eating popcorn without the butter.