Survival is no longer based upon traditional hunter/gatherer positions anymore, where being the fastest runner meant survival.
(I'm saying obese people don't tend to run very fast, or for very long.)
These days you could create an income over the internet and essentially not move for the rest of your life.
Society now fosters such things as obesity, so it will proliferate.
Obesity comes with it's own set of health risks, obviously and I'm not sure I've seen too many obese mountaineers, however surely they burn more calories due to moving more mass therefore need equal or greater intake. Unless of course they're like camels..