My FIL has Type I, and thinks that as long as he has pills he can eat and drink whatever he wants. Problem is, he's not regular on taking the pills (or checking blood sugar). He gets to where he has trouble functioning, seeing clearly, weak, etc., and then has to be prodded to take his medicine. He feels fine when he does, and crappy when he doesn't. He's a grown a-- man, why can't he learn??? It's frustrating for the rest of the family, but you can't make him take care of himself. If he feels like drinking a beer, he'll drink a beer. He has now moved across the US from us, but near a sister and her family. Hopefully they'll now watch over him and protect him from himself.
DH has a maternal and paternal history of diabetes, but tries to take care of himself so he won't end up getting it. He was told he has a 50-50 chance of it.