Outbreak of Severe Obesity and Metabolic Complications in Children and Adolescents Using the Korea National School Health Examination (KNSHE) From 2017 to 2021

Abstract

Background: This study aimed to estimate the prevalence of obesity in school children by severity and to assess the coronavirus disease 2019 (COVID-19) pandemic's impact on changes in the prevalence of obesity. In addition, the prevalence of obesity-related metabolic complications was calculated.

Methods: We used data from 390,580 school-aged children in the 2017-2021 Korea National School Health Examination to estimate the prevalence of obesity and assess secular trends in prevalence. We estimated the prevalence of metabolic complications in overweight and obese students with serological data and assessed their association with the degree of obesity, which was classified as overweight, obesity, and severe obesity per the criteria of the American Academy of Pediatrics.

Results: In 2021, the prevalence of overweight, obesity, and severe obesity among school children was 12.5%, 17.6%, and 4.9%, respectively, for boys and 10.8%, 11.9%, and 2.9%, respectively, for girls, and these values have been increasing significantly since 2017. Compared with the pre-COVID-19 period, the increase in the prevalence of obesity and severe obesity was remarkable, especially in elementary school students. The linear relationship between the prevalence of metabolic complications and the degree of obesity was evident in high school students. In elementary school students, similar relationships were found with nonalcoholic fatty liver disease and high blood pressure.

Conclusion: The severity of obesity in school-age children (especially younger children) is worsening, and this may predict an increase in the prevalence of related metabolic complications. To prevent long-term complications, it is essential to expand health screening programs.

Keywords: Metabolic Complications; Pediatric Obesity; Prevalence; Severe Obesity.

Fig. 1. Flow chart of subjects included for analysis.

KNSHE = Korea National School Health Examination, BMI = body mass index.

Fig. 2. Trends in prevalence of overweight, obesity and severe obesity by school levels, data from the Korea National School Health Examination.

The points indicate the weighted prevalence (%) at each school level. The horizontal axis represents the survey year. Overweight was defined as the 85th to 94th percentile, Obesity was defined as the 95th percentile or greater and less than 120% of the 95th percentile, and severe obesity was defined as 120% of the 95th percentile or greater or 35 kg/m² or greater. ^*P for trend < 0.05.

Fig. 3. Changes in proportion of overweight, obesity, and severe obesity from 2017 to 2021: data from the Korea National School Health Examination.

Proportion by degree of obesity were calculated for overweight and obese children. The innermost circle represents the results from 2017, the middle circle represents the results from 2019, and the outermost circle represents the results from 2021. The values in the inner circle represent the prevalence of overweight and obesity (body mass index ≥ 85th percentile).

Fig. 4. Prevalence of metabolic complications in overweight and obese children by school levels and degree of obesity.

Results are expressed as weighted percentage by integrating data from 2017, 2018, 2019, and 2021 Korea National School Health Examination. Hypertriglyceridemia and hypo-HDL-cholesterolemia were obtained using 2021 Korea National School Health Examination data. FBG = fasting blood glucose, DM = diabetes mellitus, HDL = high-density lipoprotein, NAFLD = non-alcoholic fatty liver disease, BP = blood pressure, HTN = hypertension. ^*P for trend < 0.05 across degree of obesity at each school level.