They're so fucking delusional. Even if your "bloodwork is perfect" and your "blood sugar is normal" that doesn't mean shit. At 300 pounds, you won't be "healthy" for long. All that bloodwork shows is that the human body is an amazing machine, capable of running under even drastic amounts of stress. But like any machine that you work too hard, it's going to run out sooner than it would if you had taken care of it.