Flash is a buddy of Batman, yet he does not obey his 'rule.'
Batman's 'one rule' is that he never kills his adversaries.' It is not always followed by Flash. Reverse Flash, his arch-nemesis, once attempted to murder his would-be wife, Fiona Webb. Barry became infuriated and accidentally snapped his long-time adversary's neck. Notably, Flash from the future has blown up Gorilla Grodd's skull, attempted to murder his earlier self, and even killed Wally West from the future.
Lack of exercise and obesity are the two major environmental variables for insulin resistance (and type 2 diabetes).