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Purpose: The coronavirus disease 2019 (COVID-19) pandemic has affected people's daily lives and increased their time spent at home. This study aims to investigate the changes in lifestyle factors and obesity among Korean adolescents before and during the COVID-19 outbreak.Methods: We used the data of 109,282 adolescents aged 12–18 years, from the Korea Youth Risk Behavior Survey conducted in 2019 and 2020 before and during the COVID-19 pandemic, respectively. The changes in the prevalence of obesity and lifestyle factors (diet, exercise, sitting time, and sleep duration) were assessed. The adjusted odds ratios (ORs) (95% confidence intervals [CIs]) of predictors for obesity were calculated.Results: The prevalence of overweight (10% to 10.5%) and obesity (11.5% to 12.7%) increased significantly, especially among males younger than 15 years, whereas significant differences were absent among females. The mean body mass index z-score increased from 0.28 to 0.39 in males but decreased from 0.08 to 0.04 in females. Fruit consumption, regular exercise, and average sleep duration decreased, whereas sitting time increased. After controlling for covariates, a short sleep duration (OR, 1.14) and an increased sitting time (OR, 1.14) were significantly associated with an elevated risk for overweight/obesity.Conclusion: During the COVID-19 pandemic, the prevalence of obesity and overweight increased, particularly in males, as did unfavorable trends in related lifestyle factors. Sex- and age-specific strategies to improve lifestyle factors associated with obesity are needed, especially during the COVID-19 pandemic.

Purpose This study sought to identify changes in anthropometric values among Korean school students by comparing the most recent nationwide data with previous data. Methods Data from the Korea School Health Examination Survey 2018 were used. The study population consisted of 107,954 Korean school students ranging from the 1st grade in elementary school through the 3rd year of high school. The difference in height and weight values for each sex and school grade was analyzed by comparison with the Korea School Health Examination Survey 2010. Results The mean heights of the 3rd-year high school students were 173.8 cm and 160.9 cm for boys and girls, respectively. The mean height of the 3rd-year high school students showed no difference between 2010 and 2018 for either sex. However, the mean height of the age group from the 3rd grade in elementary school through the 1st year in high school was significantly taller in 2018 compared to 2010 for both sexes. The mean weights of the 3rd-year high school students were 71.3 kg and 57.5 kg for boys and girls, respectively. The mean weight of students in 2018 was significantly higher compared to students in 2010 for most school grades. Conclusions Although no significant change was found in near-final height between 2010 and 2018 among high school seniors, the mean height during the growth spurt was significantly higher in 2018 compared to 2010. Weight was significantly higher in almost all school grades in 2018 compared to 2010.

Purpose This study was conducted to investigate the distributions of the triglyceride (TG) to high-density lipoprotein-cholesterol (HDL-C) ratio and total cholesterol (TC) to HDL-C ratio, and to explore their usefulness as markers of metabolic syndrome (MetS) in Korean adolescents. Methods We obtained data for 2,721 adolescents (1,436 boys and 1,285 girls) aged 10–18 years who participated in the Korean National Health and Nutrition Examination Surveys from 2008 to 2010. International Diabetes Federation criteria were used to define MetS. Results There were no significant gender-related differences in TG/HDL-C or TC/HDL-C ratios. These lipid ratios showed significant associations with homeostatic model assessment for insulin resistance (HOMA-IR) and waist circumference. Areas under the receiver operating characteristic curve to identify MetS were 0.947 for TG/HDL-C and 0.924 for TC/HDL-C, which were higher than that of HOMA-IR (0.822). Optimal cutoff values (sensitivity, specificity) of TG/HDL-C and TC/HDL-C ratios for MetS prediction were 3.3 (85.7%, 89.9%), and 3.8 (92.9%, 82.8%), respectively. Odds ratio (OR; 95% confidence intervals [CIs]) for MetS in adolescents with TC/HDL-C ratio above the cutoff value was 14.8 (2.8–77.4), while that for TG/HDL-C ratio about the cutoff value was 30.6 (6.0–157.6). In adolescents who had both lipid ratios above the cutoff values, the OR (95% CI) for MetS was 36.2 (7.2–186.2). Conclusion TG/HDL-C and TC/HDL-C ratios are useful markers of metabolic syndrome with high predictive value in Korean adolescents.

Phthalates are commonly used as plasticizers and vehicles for cosmetic ingredients. Phthalate metabolites have documented biochemical activity including activating peroxisome proliferator-activated receptor and antiandrogenic effects, which may contribute to the development of obesity. In vitro and in vivo studies suggest that phthalates have significant effects on the development of obesity, especially after prenatal exposure at low doses. Although few studies have examined the effects of phthalate on obesity development in humans, some work has shown that phthalates affect humans and animals similarly. In this paper, we review the possible mechanisms of phthalate-induced obesity, and discuss evidence supporting the role of phthalates in the development of obesity in humans.