>>510008986 (OP)When settlers originally came to the 13 colonies, they were largely religious and ethnic minorities fleeing persecution. They would form small, insular settler communities and build villages around them, often with a founding population barely in the hundreds.
Unwelcoming to outsiders, these communities proceeded to interbreed for roughly 200 years. There are communities in the Allegheny Mountains that remained essentially closed to outsiders until Nixon.
A consequence of all this inbreeding is an explosion of novel and otherwise exceptionally rare genetic disorders, which are now common among certain subsets and phenotypes of the american genepool. Chief among them is a family of diabetic-adjacent metabolic disorders.
These people eat high-carb food because their body constantly tells them they are starving to death, because they aren't producing enough of the proteins and hormones necessary to take the energy their body has metabolized and deliver it to their bloodcells. That unused energy instead gets taken out of their bloodstream to produce fat. They spend their whole lives starving to death while eating, and gaining weight while starving. They eat for the same reason that you can't just stop eating until you starve, overpoweringly strong hormones make the craving uncontrollable to force you to eat. But no matter how much they eat, their broken metabolism doesn't feed enough of that energy to their cells, so their body still tells them it's starving to death, and they keep eating.
When you get one of these people to slim down, their quality of life declines, because now instead of being morbidly obese they just suffer from chronic anemia and hypoxia. And when you run bloodtests you always find that these people are actually a timebomb of a dozen different recessive genetic disorders that are normally rare, but common in their state because they're a product of a dozen generations of reverse-eugenics.