It's made worse by the fact that when people give up on losing weight (and most people that fail to do so eventually will give up), they tend to give up by givi

It's made worse by the fact that when people give up on losing weight (and most people that fail to do so eventually will give up), they tend to give up by giving in to their own stereotype - eating buckets of fried chicken and guzzling soda. They've created a scarcity reaction in themselves by avoiding all the unhealthy crap that is out of proportion to the actual hardship involved - psychology is a messy business. So then people see them indulging themselves and think "No wonder he's so fat, look what he eats", and confirmation bias gives them a nice hug.