The rise of childhood obesity in less developed countries is often overlooked. The authors study the impact of body weight report cards in Mexico. The report cards increased parental knowledge and shifted parental attitudes about children's weight. The authors observe no meaningful changes in parental behaviors or children's body mass index. Interestingly, parents of children in the most obese classrooms were less likely to report that their obese child weighed too much relative to those in the least obese classrooms. As obesity rates increase, reference points for appropriate body weights may rise, making it more difficult to lower obesity rates.