My grandparents are not obese, they are there because they are old and can't take care of themselves and have dementia, just like all the other people there. All of them are old, only some are fat, so this argument you are conjuring about fat people in nursing homes is simply bullshit. Once you are past 60 you are rolling the dice, there are all sorts of conditions that land you in that home. Good for that 80yo dude you ran with, but he is an outlier. As a wise man once said, "You see plenty of young runners people in the streets. And plenty of old people. But you rarely see old runners." Did you expect to see tons of old fat people at your marathon? There is nothing wrong with an old, healthy person having other hobbies, reading, gardening, etc. Of course that one old dude is going to seem like an inspiration. Remember that no how much you respect that old man, he is still going to end up with a nurse wiping his ass, don't pretend like running a marathon now and then is going to save anyone from that fate.