I get that you are observing the dictates of political correctness, but it is decidedly foolish to believe that all races or people must be equal. Nature does not worship at the alter of PC even if you do. Genetics dictate a great deal of a person's intelligence and health and ones race dictates ones genetics Madam Oblivious. Save that for snowflakes.No, we don't know. "Genetics" in this case is just another way of shrugging and saying, "Don't know why".
I could get you a detailed explanation of EXACTLY what happens in the human body as it grows obese to cause it to develop diabetes. But no one as yet can give you a similar explanation of why a BLACK body is more likely than a white one to get diabetes under the same circumstances. Simply saying, "genetics" at that point is like saying, "because he's black". Thanks, Captain Obvious, but that's not helpful.