It's also very difficult statistically to remove the co-morbidity factors:

populations that eat more "processed" foods !especially in the US! are poor, in toxic environs, stressed, over-policed, incarcerated, discriminated, unstable housing healthcare employment, using "coping" mechanisms, in a food desert, multigenerational defecit of various "health skills", no "free" time for cooking and exercise, etc etc etc

If they had healthcare, housing and union jobs ... stats wouldn't be near so bad for them