S1 Dataset -

Objectives
Weight perceptions have been implicated in weight control related behaviors among children and adolescents, yet studies in mainland China are scarce. We examined the associations of self-perceived weight status and weight misperception with weight control related behaviors in Chinese middle and high school students.
Methods
We used cross-sectional data from the 2017 Zhejiang Youth Risk Behavior Survey which that included 17,359 Chinese students, with 8,616 boys and 8,743 girls. Perceived weight status, as well as height, weight and weight control related behaviors information was collected via a self-reported questionnaire. Odds ratios (ORs) with 95% confidence intervals (CIs) calculated by multinomial logistic regression were used to assess the relationships between weight perceptions and weight control related behaviors.
Results
Among the 17,359 students aged 9 to 18 years, the mean (SD) age was 15.72 (1.64) years. Overall, 34.19% of children and adolescents perceived themselves as overweight and the prevalence of weight misperception was 45.44%, with 35.54% overestimation and 9.90% underestimation. Children and adolescents perceiving themselves as overweight were more likely to have weight control behaviors, with OR was 2.60 (95% CI: 2.39–2.83) for weight control attempt, 2.48 (2.28–2.70) for exercising, 2.85 (2.60–3.11) for dieting, 2.01 (1.51–2.68) for taking laxatives, 2.09 (1.67–2.02) for taking diet pills, and 2.39 (1.94–2.94) for fasting, respectively, compared to those with right weight status. Among children and adolescents with overestimating weight status, the OR was 2.40 (2.22–2.59), 2.50 (2.31–2.70), 2.85 (2.61–3.11), 1.81 (1.39–2.37), 2.20 (1.77–2.74), and 2.16 (1.77–2.63) for weight control attempt, exercising, dieting, taking laxatives, taking diet pills, and fasting, relative to those with accurate weight perception.
Conclusions
Self-perceived overweight and weight misperception are prevalent in Chinese children and adolescents, and positively associated with weight control related behaviors.