I answer this in a few ways. First, it is an absolutely unrefutable fact that I am going to die. It might be a massive coronary that kills me, or it could be a runaway bus headed in my direction. I don't get to choose how and when I will die, so I try not to worry about it. Second, it's an odds game.
Many obese people live to ripe, healthy old ages.
I know this is true because there are many of these people in my family. One's overall constitution is a marvelous factor, and I am a pretty tough woman. I do not weigh 700 pounds nor am I bedridden. After all, as mentioned above, anorexia and bulimia kill and probably in a more immediate fashion than does my weight. I showed my tendency to fat early.