I provide novel evidence on the role of imperfect information in shaping childhood obesity. Between 2003 and 2017, 24 states began requiring schools to perform Body Mass Index assessments on students. Using the 1991 to 2017 National and State Youth Risk Behavior Surveys and a stacked difference-in-differences identification strategy, I show that these state-mandated school-based BMI assessments were associated with an increase in the likelihood that teens described themselves as overweight and reported that they were trying to lose weight. The relationship was most pronounced for overweight teens, suggesting that the assessments improved awareness about BMI status among this group, though I also find that non-overweight teen girls were subsequently more likely to incorrectly describe themselves as overweight. While I do not detect meaningful changes in exercise or calorie-limiting behaviors, I do find that these state-mandated school-based BMI assessments were associated with a modest reduction in BMI.

中文翻译：

---

国家规定的基于学校的 BMI 评估和自我报告的青少年健康行为

我提供了关于不完美信息在塑造儿童肥胖方面的作用的新证据。 2003 年至 2017 年间，24 个州开始要求学校对学生进行体重指数评估。使用 1991 年至 2017 年国家和州青少年风险行为调查和叠加的双重差异识别策略，我发现这些州规定的基于学校的 BMI 评估与青少年描述自己超重和肥胖的可能性增加有关。报道称他们正在努力减肥。这种关系在超重青少年中最为明显，这表明评估提高了该群体对 BMI 状况的认识，尽管我也发现非超重青少年女孩随后更有可能错误地将自己描述为超重。虽然我没有发现运动或热量限制行为发生有意义的变化，但我确实发现这些州规定的基于学校的 BMI 评估与 BMI 的适度降低有关。