and that it's not reverse-causal.  What do you mean? Type 1 is mostly genetic, but can be prevented with good diet. Type 2 is from shit dieting constantly spiking blood sugar making you become insulin resistant. Type 2 is reversible.   Normalisation of both beta cell function and hepatic insulin sensitivity in type 2 diabetes was achieved by dietary energy restriction alone. This was associated with decreased pancreatic and liver triacylglycerol stores. The abnormalities underlying type 2 diabetes are reversible by reducing dietary energy intake.   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3168743/ So by reducing the amount of kcal consumed, that leads to type 2 diabetes disappearing. Type 1 is mostly genetic. If type 1 runs in your family, you most likely will get it, but it is preventable through extra measures.