Totally off-topic, but I wish people could realize just how hurtful comments like these can be to people who are just extremely thin (like my daughters). It's just as insulting, yet for some reason it's socially acceptable to bag on thin people. The only real true difference is that my kids couldn't get any heavier if they tried. It's just not how they're made. My youngest is about 5 feet tall and is just over 70 lbs. It's how she's built. She gets insulted all the time for how skinny she is and no one ever considers that it is just as hurtful as calling someone that's overweight "fat".
When she's older, she may fill out some, but for now, she's just super skinny. Doesn't mean she has an eating disorder, although she gets accused of it.