If you were a carnival weight guesser, do you think you would do a good job?
I had to weigh people in for a weight loss contest at work and it was really eye-opening for me. I played a game in my head and tried to guess before the people weighed in, just to see if when I do the "where do I rank, bodywise?" thing in my head if I was on target. Generally, I was pretty close with people who were obese/morbidly obese. But when it came to thinner people, not so much. One girl was fussing about how she had gained weight and I wasn't bothered by it (which I once would have been), but I still thought that she weighed significantly less than I do. I actually weighed 8 pounds less than she did.
It's not often that you get to know if you're right about someone's weight, so this might be pure speculation, but I thought it would be interesting.