Well, it's definitely correlated with the time we've decided that "fat is bad, eat low fat for better health" that we've gone from obesity being a rare metabolic syndrome to a widespread epidemic. And the increased reliance on processed food, which is not only the very maligned ultra palatable junk food, but processed food in general.

Of course it's more complicated than that, studies are moving in that direction but it's going to be 50 more years since updated dietary guidelines become common (grandma's) knowledge.