There's also the issue of undetected chronic conditions. Congenital heart defects are pretty common, and quite often go undiagnosed right up until someone has a heart attack. That's not the free pass fatties want to make it out to be though. Because one of the biggest factors there for whether one can actually survive it or even have the problem detected before it becomes life threatening is being in good shape. The fit 30 year old who has a heart attack at the gym is going to have far better chances of getting through it than if he'd been obese and triggered that same event at 20.