Do they, or do they just get diagnosed then? I would suspect that weight gain and predictable "slowing of metabolism" have something to do with it. Toss in a decline in beta cell population and there you have it.There is a strong consensus among the medical community that genetics play a significant role in why people become type 2 diabetics. Type 2 diabetes appears mainly in the middle age normally after the age 40. (Nowadays, many young people, some even in their teens are diagnosed type 2 but it is still an exception to the rule.) Why is it that the genes responsible for type 2 diabetes choose to "express" themselves mainly after age 40?