I've known a few and they all have the same thing in common: they all eat a high carb/low fat diet.
I also don't understand why they ignore the phenomena of people magically becoming non-diabetics after gastric bypass. Some of these people recover normal blood sugars after only a couple of days. Way too fast to be related to weight loss.
IMHO, insulin resistance is caused by a combination of diet, genetics and hormones.
I think in a lot of cases Polycystic Ovarian Syndrome is also said to bring on insulin resitance. This affects many, many, women.