McDonalds started selling hamburgers and french fries in 1940. Watch what happens with cardio vascular disease as a leading cause of death starting around then:
Then again, Sony started up after WWII so maybe heart disease is caused by Sony products? [sarcasm]
As hygiene and water purification plants across the US proliferated many diseases dwindled off and people started living much longer so diseases which take time to develop (like clogged arteries and some cancers) may appear to have "grown" but its largely that we live longer now.
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I just figured out what causes obesity so I think I'll right a book about it. It's proximity to the Mississippi river:
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