Childhood and adolescent obesity is one of the most serious global public health challenges affecting every country in the world [1]. There has been increasing awareness on the health of children and adolescents because growth and development during childhood and adolescence significantly impact lifelong health and well-being. In particular, obesity during childhood and adolescence has been shown to increase the risk of overweight, obesity, and various non-communicable diseases in adulthood, and it might also contribute to children’s poor educational outcomes [2].

As global obesity rates continue to rise, certain regions have experienced particularly rapid changes, underscoring the need for focused public health interventions. The regions with the largest increases in such incidences are East Asia, the Middle East and North Africa, South Asia, and other high-income English-speaking areas [3]. The rapid economic development and urbanization in East Asian countries like China (People’s Republic of China, PRC), Japan, South Korea, and Taiwan (The Republic of China, ROC) have led to profound shifts in dietary habits (e.g., increasing consumption of fast food, processed foods, sugary beverages) and physical activity levels (e.g., increased screen time, reduced physical activity due to urban environments) [4]. These changes have contributed to growing prevalence rates of overweight and obesity among children in this region. Simultaneously, other weight-related issues, such as thinness, continue to persist, adding complexity to the nutritional and health challenges faced by some countries’ children [5]. While these East Asian countries undergo similar societal transformations, disparities exist in cultural awareness and policy implementations within each nation. However, cross-country comparative research has been limited.

To better understand the current trends and challenges, it is critical to examine the weight distribution among children across East Asia, including the prevalence rates of thinness, normal weight, overweight, and obesity. Due to differences in obesity definitions and country-specific growth charts, direct comparisons of obesity prevalence across countries may not be appropriate. This study sought to analyze the weight trends among children aged 5 to 19 in China, Japan, South Korea, and Taiwan using data from the Non-Communicable Disease Risk Factor Collaboration (NCD-RisC). By utilizing World Health Organization (WHO) criteria and applying statistical methods, this research will provide insights into the evolving patterns of pediatric weight status in the region, highlighting areas of concern and the need for targeted public health interventions. This study also aims to inform policymakers, healthcare providers, and educators involved in government policy on food marketing and physical activity, community-level initiatives, and school-based programs about the importance of addressing the trends of pediatric obesity and thinness, emphasizing the need for comprehensive, region-specific strategies to improve the health and well-being of East Asian children.

According to the WHO fact sheets, the prevalence of overweight (including obesity) among children and adolescents aged 5 to 19 had risen dramatically from 8% in 1990 to 20% in 2022 worldwide. The rise has occurred similarly among both boys and girls [7]. Pediatric obesity does not naturally resolve as the child grows. However, it instead persists into adulthood, with various physical and psychological complications before adulthood, and strongly predicts adult weight status and future health outcomes [8].

Underweight as well as obesity can lead to adverse health outcomes, both immediate and long-term. This condition is associated with poor academic performance, impaired physical growth and developmental milestones, anemia, respiratory failure, wound complications, extended hospital stays, and increased vulnerability to infections and diseases [9]. Persistent thinness during adolescence is associated with an increased risk of adverse health outcomes, such as chronic diseases, impaired physical development, and an increased risk of all-cause mortality later in life [10]. The double burden of malnutrition (DBM), defined as the coexistence of both undernutrition and overnutrition in the same population within communities, families, and even individuals across the life course, continues to be a major global public health problem [11, 12]. The DBM occurs at an individual level, such as in cases in which children with undernutrition are later exposed to high-calorie food and develop obesity [13]. The growing evidence of the DBM suggests that comprehensive policy efforts are needed to address the issues of undernutrition and obesity simultaneously [14]. In almost all countries for adults, school-aged children, and adolescents, the increases in double burden were driven by increases in obesity and decreases in double burden by declining underweight [5]. Analyzing the trends in childhood obesity and underweight is crucial for developing effective preventive and management strategies for children’s health.

The people in the regions of East Asia, including Chinese, Japanese, South Korean, and Taiwanese, belong to the Mongolian race [15]. Chinese, Japanese, South Korean, and Taiwanese share certain physical and genetic characteristics because of their geographical proximity and historical interactions and exhibit similar physical characteristics and disease susceptibilities.

The pronounced differences in the Asian population include the high proportion of body fat and predisposition to visceral fat accumulation and subsequent abdominal obesity compared with Caucasians, leading to an increased risk of diabetes at lower BMI levels in Asians [16, 17]. However, each country has different genetic backgrounds and distinct cultural variations, including dietary patterns and physical activity levels influenced by lifestyle, education, and urbanization, while healthcare infrastructure, preventive care, and government initiatives also significantly affect obesity prevalence. In Japan, since the late 2010s, annual percentage changes of pediatric obesity have significantly increased in 12 to 14-year-old boys (6.7%–8.9%) and girls of many age groups (2.6%–8.6%) [18]. In South Korea, the prevalence rate of obesity in children and adolescents surged from 9.7% in 2012 to 19.3% in 2021, with a greater increase in boys [19]. China, a vast country with regional disparities in socio-economic conditions, dietary habits, and lifestyles, has remarkable regional differences in obesity rates among children and adolescents [20]. The prevalence of overweight and obesity among children and adolescents aged 7 to 18 years had soared from 5.3% in 1995 to 24.2% in 2019, affecting almost a quarter of children and adolescents in China [21]. In Taiwan, the prevalence of obesity had increased from 13.19% in 2009 to 14.97%, and the prevalence of overweight had declined from 13.17% in 2009 to 12.63% in 2018 [22]. The use of country-specific growth charts in diagnosing childhood obesity is essential due to variations in growth patterns among children and adolescents in different countries. China, Japan, South Korea, and Taiwan have developed their growth charts tailored to their populations [23–26]. Thus, this study aimed to analyze the changes in weight distribution and compare the prevalence and trends of pediatric obesity in East Asian countries using WHO criteria.

Our analysis revealed significant shifts in the prevalence of underweight, normal weight, overweight, and obesity in East Asian children and adolescents from 2010 to 2022. Overweight and obesity have been on the rise in East Asia, with particularly rapid increases in South Korean boys and Chinese girls. In 2022, the overweight and obesity rates were the highest in South Korea (girls: 24.6%, boys: 43.0%). The sharp rise in obesity among South Korean boys and Chinese girls is alarming and underscores the need for targeted public health policies and reassessment of current management strategies. Japan exhibited the least change in overweight and obesity rates. Taiwan showed a less pronounced change, although the absolute prevalence remains high, indicating a potential stabilization but not necessarily an improvement in public health outcomes. The traditional Japanese diet, characterized by its abundance of seafood, vegetables, and fermented soy products, coupled with its low consumption of calorie-dense, minimally seasoned foods, frequent home-cooked meals, and small portion sizes, along with the distinctive divided meal system, may contribute to the notably low obesity prevalence in Japan [27]. Moreover, according to a comparative analysis of physical activity in East Asian countries from 2016 to 2022, South Korea and Taiwan had experienced no changes in overall physical activity, while China had shown improving levels of physical activity, with no notable changes in governmental policies. Japan exhibited improvements in physical fitness, active transportation, community, and the environment, along with stable levels of sedentary behavior, with moderate governmental policies throughout the period [28].

The prevalence rates of overweight and obesity have consistently been higher in boys than in girls across all countries. The gap between the sexes widened significantly in South Korea and Japan. For instance, the gap in South Korea had increased from 11.9%p in 2010 to 18.4%p in 2022. In high and upper-middle-income countries, boys tend to have higher obesity prevalence than girls, but the possible reasons and implications of this difference are yet to be fully understood [29]. The difference in prevalence of childhood and adolescent obesity between sexes may be driven by biological and sociocultural influences, like body composition and gender-based stereotypes [29, 30]. Thinness has also been an issue in East Asia, with notable increases observed in Taiwan and South Korea. The increase in thinness in Taiwan is particularly significant, suggesting a growing public health concern. In contrast, China had exhibited a decrease in thinness among both girls and boys. While China shows a pattern of increased obesity accompanied by decreases in underweight, normal weight, and overweight categories, South Korea exhibits a pattern in which the increase in obesity is accompanied by an increase in underweight prevalence. In Taiwan, the increase in obesity had not been as rapid as exhibited in other countries; however, similar to South Korea, there had been an accompanied increase in the prevalence of underweight individuals. Such discrepancy among countries highlights the need for country-specific strategies. South Korea and Taiwan need to focus on preventive and management policies for DBM. China, on the other hand, may need to concentrate more on policies addressing the increasing rates of overweight and obesity.

The prevalence rates of children and adolescents with normal weight have decreased across all countries. Out of all weight categories, the normal weight rate was the highest, suggesting relatively effective weight management strategies among East Asian countries. Conversely, Korea had displayed a sharp decline in normal weight prevalence in boys (-10.0%p), indicating an increasing trend towards either underweight or overweight and obesity. This shift is a growing public health issue that requires urgent interventions to promote healthy weight management. Healthy weight initiatives should approach the weight spectrum as a whole, not focusing on certain weight categories [10].

Comparing the distribution of obesity among age groups can pinpoint the ages most vulnerable to obesity, allowing tailored interventions for susceptible age groups. Though there has been a lack of reports on childhood obesity that classify age groups in a one-year interval, some studies have utilized a relatively short interval span of five years. In a US study, data were classified by sex and age (2 to 5, 6 to 11, and 12 to 19 years). From 2003 to 2004 and from 2007 to 2008, the 6-to-11 age group had the highest obesity prevalence, whereas from 2005 to 2006, the 12-to-19 age group had the highest obesity prevalence [31]. In a study conducted in China, the highest prevalence of obesity was observed in 12-year-olds for both sexes, suggesting a need for interventions before 12 years of age [32]. According to another study conducted in West Asia, the prevalence of obesity was the highest in the youngest age group (2 to 6 years), followed by the oldest age group (14 to 19 years); the lowest was in children aged 7 to 13 years [33]. Our study showed the prevalence of overweight and obesity has been the highest in children aged 10 to 11 years in all countries. It is important to note that the diagnostic criteria for overweight and obesity in adults in Asia (BMI 23 and above) do not align with the criteria for overweight and obesity in children and adolescents (BMI at or above the 85th percentile). This discrepancy leads to an underestimation of obesity rates in late adolescence, further emphasizing the necessity of treatment of childhood overweight and obesity. Our results, thus, suggest that the normalization of body weight before the onset of puberty is crucial.

There are some limitations in our study. First, estimating the prevalence rate of pediatric obesity using a national reference may better capture the prevalence rates of overweight and obesity in each country. Though our study calculated obesity prevalence based on WHO standards for comparison among nations, there may be a difference from the obesity prevalence calculated using the growth standards of each country. Second, to compare the prevalence rate of obesity across multiple countries over time, studies must consider various factors at multiple levels, from a national level, such as national policies and childhood obesity programs curriculum, to an individual level, such as socioeconomic factors, parental education, and nutritional supplies. However, due to limitations in the available data, analyzing such demographic factors was challenging.

Despite the limitations of this study, to the best of our knowledge, our study is the first to compare the recent prevalence of pediatric obesity and the change in weight distribution in East Asian countries, utilizing uniform criteria.

The trends in the prevalence of thinness, normal weight, overweight, and obesity among East Asian children and adolescents underscore a growing public health challenge. The significant increases in overweight and obesity, particularly among South Korean boys and Chinese girls, are alarming and call for urgent public health interventions. Attention should also be paid to the trend of increasing thinness of children and adolescents in South Korea and Taiwan. Additionally, the declining proportion of children with a healthy weight in all countries is another concerning issue. Addressing these trends will require a multifaceted approach, including promoting healthy dietary habits, increasing physical activity, and implementing effective public health policies. The varying trends across different countries and gender groups also highlight the importance of tailored strategies to address the unique challenges faced by each population segment. Considering the age distribution of obesity, intervention for obesity would be preferable before the age of 10 to 11. Further research is essential to explore the underlying causes of these trends and develop targeted interventions that can effectively combat childhood and adolescent weight issues in East Asia.