It's going to be multifactorial, of course, with fiat food playing its part (low copper), plus seed oils, etc. I think iron dysregulation (caused by low copper) is where all the problems lie, with insulin being affected, leading to diabetes. Studies have shown that reducing iron levels can improve glycemia in T2DM patients, suggesting a causal link between iron and diabetes.

Throw in stress affecting iron regulation, and we have a strong framework for my approach to eating. I came off TRT after being on it for 10 years, and after allowing my body to reset, I'm feeling just as good as when I was taking testosterone. So many other things are improving too.

https://www.sciencedirect.com/science/article/pii/S1550413113000557