Diabetes is actually more of a continuum than a pair of diseases. I was diagnosed with a Type 2 variant (low insulin output and high insulin resistance) when I was in my twenties, and I was very skinny at the time. I can't tell you how offensive it is when people (including many Type 1s) blithely blame Type 2 exclusively on lifestyle choices. That said, diet and exercise do work very well to control Type 2 diabetes.