I have friends that can eat the SAME EXACT thing as me and they stay forever skinny (not more active than I am) while I am a little over weight AND have diabetes. Even from the same parent I see a fat twin and a skinny twin, or a pretty and an ugly one... I'm definitely not a geneticist either! But I do find it very intriguing since I started raising and breeding chickens. And completely agree not breed forward bad genetics.
With the calcium overload people talk about causing kidney failure in some... that is also a genetic predisposition.
I did just research if NAFLD (non alcoholic) was genetic or not. It appears that it can be but is ALSO heavily influenced by LIFESTYLE. Being at a higher risk for something doesn't mean you will develop it. With my diabetes (type 2 for more than 22 years now) I have a "higher risk" of developing heart disease, hypertension, and whole host of other things. Even though I binge sometimes and have some issues, my mother in law who "eats right" still has hypertension AND high cholesterol.
So I might go out on a limb and say that it could very well be a combination of lifestyle AND genetics.  
How many sudden deaths that occurred from this cause were linked to "it just happens" or "it was probably a heart attack".
I never knew this was a possibility, but now it's on my radar! I wish there were more obvious symptoms.