Let's not forget genetics. My two parental sets are from immensely different body types, yet raised in the same locale and with similar food sources and work. Both farm families.

Between them there were 18 children, 12 giants and 6 tinys. The giants all went to fat and T2D. None of the tinys did. All the giants are deceased. Four of the tinys are still living, two in their 90s.

I go with the theory of a combination of genetic makeup, what I call "early dietary intervention," and food additives, especially high fructose corn syrup.