I will be lazy and let Dr. Sharma explain what I think is really going on with many "genetic" explanations...
Now imagine that people with a high genetic risk, a moderate genetic risk, a substantial genetic risk and a severe genetic risk for asthma were all living out in cottage country, where there is clean air with no air-borne dust or pollutants. Only those few individuals unfortunate enough to have ’severe’ genetic risk would have asthma - everyone else would be perfectly fine.
Researchers studying the relationship between asthma and genetics in cottage country would find that in most people genes have no effect on asthma symptoms and only in people with very severe asthma would there appear to be some genetic influence.
Now imagine that a busy highway is built straight through that community with lots of heavy car and truck traffic that significantly reduces air quality.
Now, even those with low genetic risk will start wheezing, those with moderate risk will start coughing, those with substantial risk will no longer be able to do heavy work outside, and those with the most severe risk will be confined to their beds under an oxygen tent.
Suddenly, researchers studying this community, will find that there is a close relationship between genetic risk and asthma symptoms - indeed, the difference between those who have no, some, moderate, substantial or severe asthma can almost entirely be explained by genetics. In fact, in those with any symptom of asthma - the entire ‘variance’ will be found to be almost completely attributable to their genetic risk - suddenly genes become the most important determinant of who has symptoms and who doesn’t!>
Certainly there is a genetic component to diabetes. This seems to be true for both Type 1 and Type 2. However, as with asthma, which by some resports has seen a 75% prevalence rise in not so many years, as well as obesity, there is also great evidence of very strong environmental factors.
Does this nullify genetic risk? Certainly not. Does it mean that whether the genetic tendency will be expressed has a great deal to do with envoronmental exposure? Absolutely, IMHO.
I think we know what "environmental exposure" means relative, especially, to Type 2 diabetes.