I too wasn't what most people would call obese, but on BMI, I was. I'm not any more. BMI makes out even not very heavy people are obese ie BMI 30 For my height of 170cm that's 87kg or about 13 1/2 stone. By no means huge.
there's little doubt that weight problems and T2DM are LINKED. My own theory is that the weight thing is a symptom, not a cause. Insulin resistance is a feature OF T2DM and a high level of circulating insulin causes weight gain as insulin users often find out.
However, A link is not proof of causality. Making it seem so is BAD SCIENCE.
I also suspect that insulin resistance results from trying to keep to the recommended Healthy Balanced Diet, high in carbs. That triggers the problem in susceptible people. I feel it's no co-incidence that the rise in cases of T2DM links in with the adoption of a low fat way of life in most of the developed world.
Neverthelesws, i ccannot prove that this is a case of cause and effect. I CAN show a LINK [Gary Taubes has done just that]
Hana