I was sitting in the same room at a church activity that draws young people, with a group of girls who were mid-teens to 18 or so, who had been friends since they were children, who were having a typical teenaged girl conversation. One of the girls was outstandingly tall, with the large bones and extra weight of her parents. When one of the smaller built girls whined about being 'fat', the heavy girl tried hard not to take it personally, but I knew she wanted to shrink out of that moment.
When I had a chance for a private moment with the girl complaining about being fat, I asked her how she thought it made her other friend feel, I knew she was sincere when she said she just never thought about it like that. I knew her better than I knew the other girls so I just asked her to slip a word to the others to think about how it makes truly overweight people feel to have thin people whine about being fat.
I think it helped. They just don't consider others' perspective sometimes.