The fallacy in your thought is that those who lived to be 90+ did not experience prolonged overabundance of both food and leisure/sedentary lives.
The diabetic epidemic if there is one is experienced by the children and grand children of those of whom you speak.
Their lives were more like humans of old who lived lives requiring more exercise just to live and who did not have Doritos or all the chicken and meat and fries and..... they could want. The problem with abundance is that it is contrary to the genetic programming of tens of thousands of years of evolutionary biology.
I’m a few months away from 70. My grandmothers cooked with schmaltz, added chicken skin cracklings to everything meat based and sour cream and butter to everything dairy based. Both were prolific bakers and used pounds of butter per week.
They were both obese even though they were born in the 19th century and gardened, cooked and baked from scratch, sewed, did their own cleaning. They did not exercise or even walk much. They both developed Type 2 and died of stroke or heart attack in their 50s/early 60’s. One smoked. The daughter of the one who dies at 60, my mother, is still alive at 95 and smoked for 20 years. My Dad was always a good weight, never exercised much after the 1950s and died of a heart attack (his 3rd) at 84. He smoked for 55 years.
My mother did not garden, did not exercise after 40 and cooked the same way as her mother, with a few years of low fat in the mix. The Depression did not mean starvation for my family. I’d say they had an overabundance of leisure expressed in weekly card games, including afternoon Canasta and Ma Johng and evening poker, parties, *functions*, movies, the occasional cruise or casino outings, winters in Arizona.
None of my sibs or surviving cousins are fat or have Type 2.
We are all 65-73 and were more active aged 30-65 than our parents. We have abundance and some have it in spades. The ones who are dead died young of specific diseases beyond lifestyle control.
I think it is just the luck of the draw.