Objective  To examine the distribution of body mass index (BMI), the consistency between self-evaluation of body weight and BMI category and to explore the impact of the self-evaluation on relevant behaviors among senior high school students in Nanchang city of Jiangxi province for providing evidences for the development of targeted health education on correct self-evaluation of body weight in the students.

  Methods  We conducted a self- administered anonymous questionnaire survey among 884 senior high school students recruited in 5 high schools with stratified random cluster sampling in Nanchang city during June 2015. Youth Risk Behavior Surveillance System (YRBSS) was adopted to collect information on main health risk behaviors and BMI was calculated based on self-reported height and weight among the students.

  Results  Of all the respondents, 52.38% reported the self-evaluated body weight in line their BMI categories; 26.24% overestimated their body weight; and 21.38% underestimated their body weight. There was a statistically significant difference in planned body weight control behaviors in the respondents reporting the body weight inconsistent with their BMI categories (χ² = 239.019, P < 0.001). Multivariate nonordinal logistic regression analysis demonstrated that planned weight loss was correlated positively with overestimated body weight (odds ratio OR = 4.972, P < 0.001) but inversely with underestimated body weight (OR = 0.234, P < 0.001) and the female respondents were more likely to overestimate their body weight (OR = 2.369, P < 0.001).

  Conclusion  Correct self-evaluation of body weight is of great significance for growth and development in adolescents. Correct self-evaluation of somatotype is beneficial to promote healthy dietary and physical exercise behavior; while, inaccurate self-evaluation of somatotype could lead to improper weight loss practice in the adolescents.