Are you aware that some scientist are pursuing a theory that DM type 2 is what may actually be making some people overweight? That the DM in its earliest stages causes the pancreas to produce excessive levels of insulin, thus driving blood sugars low which results in increased hunger. This increased hunger results in overeating resulting in weight gain which causes worsening DM symptoms.
I'm not saying that is the reason for all type 2's. Just a counterpoint to your post. The fact remains that no one knows what exactly causes type 2 DM. If it was just weight, then a lot more people would suffer this illness than actually do.
Personally I think weight contributes to DM, not DM causes the weight gain, but scientist are pursuing both paths.