1st grader having weight issues already!!!?

My 6 yr old daughter is in 1st grade, and comes home telling me she has to lose weight. She is in great health, and in healthy average for weight. She has an athletic built, I'm uming genetics, and is very active in sports. She is mostly muscle. Her calves and legs are thicker than most kids, along with her backside. I ask her why she feels she needs to lose weight, she says because she thinks she is fat. I ured her she is beautiful, not fat, and a great kid. I ask her if kids at school tease her she says no. I have no clue where she could possibly get the idea that she is fat. She is wonderful, and has a body I wish I had. Is this normal for kids now days to feel self conscious about themselves, and weight? Is society putting too much pressure on our little ones, to make them feel they have to look a certain way? I'm not sure what else to say or do for her. I'm not putting her on a diet, no reason to, and she is in sports so she gets exercise. HELP she is too young and beautiful for this.