This study aims to assess the trends in the proportions of weight loss efforts among Korean adolescents aged 10–18 years from 2005 to 2021, examining variations based on weight status, to examine factors related to weight loss efforts by weight status, and to evaluate weight loss efforts based on the combination of measured and self-perceived weight status.

Complex sample design analyses were conducted on a dataset comprising 10,760 adolescents, utilizing information from the Korea National Health and Nutrition Examination Survey, a nationally representative dataset. Participants were categorized into non-overweight and overweight groups using a BMI percentile threshold of 85.

22–29 % of non-overweight adolescents and 54–77 % of adolescents with overweight engaged in weight loss efforts. Among adolescents who attempted to lose weight from 2005 to 2017, 39.5–57.1 % tried both of diet and exercise, 22.7–47.4 % tried exercise alone, and 10.2–26.7 % tried diet alone. Female gender, older age, and higher self-perceived weight status were associated with increased odds of weight loss efforts, irrespective of actual weight status. For adolescents perceiving themselves as obese, the odds of attempting weight loss were 8.32 for non-overweight boys, 2.02 for non-overweight girls, 15.28 for overweight boys, and 5.77 for overweight girls compared to controls who were non-overweight and perceived themselves as not obese.

Weight loss efforts among Korean adolescents aged 10 to 18 remained consistent irrespective of their actual weight over 16 years. Throughout this period, adolescents who perceived themselves as obese were more likely to attempt weight loss, independent of their true weight status. Hence, subjective weight perception plays a significant role in influencing weight loss behaviors among adolescents.