As the obesity has been considered as a global public health issue, the obesity rates in South Korea have grown constantly for the last 10 years. According to the 2012 Korea National Health and Nutrition Examination Survey, the obesity rate among adults increased from 25.8% in 1998 to 32.8% in 2012 [1]. The obesity rate among children and adolescents also grew significantly, from 5.8% in 1998 to 15.3% in 2013 [2]. Moreover, according to a recent analysis of over 100 million health checkup cases in a big data study from the National Health Insurance Service, severe (BMI≥30) and morbid obesity rates (BMI≥35) increased 1.7- and 2.9-fold, respectively, in the last 10 years, higher rates of increase than the overall obesity rate [3]. These changes vary according to age and gender, which implies the need for targeted management plans.

Obesity increases the incidence and mortality of various chronic diseases such as hypertension, cardiovascular disorders, and diabetes. In particular, Asians tend to have higher fat ratios in their bodies even though they have lower weight or abdominal circumference than Caucasians, which increases their risks for chronic diseases due to obesity [4]. Accordingly, obesity increases individual medical uses and health expenditures [5], and the rising obesity rates also increase social costs. Total medical expenditures for 23 obesity-related diseases in South Korea increased to 12.7 trillion Korean won (KRW) in 2011, a 45.1% increase since 2007; similarly, national health insurance expenditure also increased by 40.5% to 2.9 trillion KRW in 2011 compared to 2007 [6].

Studies on obesity determinants and prevention and management strategies have mostly been conducted in North America where obesity was first described as a social problem. Recently, with increasing interest in obesity as a key public health issue in South Korea, more research has been conducted in various fields of study. However, most of these studies focus on individual factors, without an integrated perspective that includes interactions between individuals and their environments. Furthermore, many studies have been in small-scale, without sufficiently large sample sizes to be representative of populations [7].

Obesity is generally caused by an imbalance between caloric intake and consumption. However, the causes of obesity are still not clearly defined; it is determined by complex and multidimensional factors including genetics, health-related behavior such as diet and physical activity, and psychological and socioeconomic factors [8]. Previously, the causes of obesity were reported as individual genetic factors and health behaviors from a biomedical perspective; however, recent research on the complex causes of obesity has resulted in renewed discussions on the impacts of various environmental factors that are hypothesized to have a greater influence on obesity than genetic ones have [9-11].

The socioecological model offers a theoretical basis for the analysis of complicated and multidimensional factors that affect the obesity, as well as for the promotion of effective policies for its prevention and management [12]. Since individual behaviors are affected not only by individual beliefs but also by the surrounding environments, this model emphasizes the need to consider environmental factors and establish strategic guidelines to change those factors when implementing intervention strategies to change individual behavior [13].

As such, various articles have emphasized the need for a multidimensional approach in studies on health promotion and behaviors. Moreover, many researchers and policy makers are interested in developing comprehensive and multidimensional interventions and policies based on a socioecological perspective. In particular, strategies to solve various health problems discussed by international organizations including WHO since the 2000s as well as national health strategies deployed in the US such as Healthy People 2020 emphasize a socioecological approach that considers complex individual and environmental aspects.

Thus, this study aimed to explore multidimensional factors related to obesity by dividing them into individual and environmental factors based on the socioecological model, and to investigate the effects of community environment on obesity by applying multilevel analysis.

This study evaluated factors affecting the obesity of individuals from a socioecological perspective by dividing the factors into individual and regional levels. It found that individual-level sociodemographic characteristics were significantly related to obesity, and varied according to gender. Men generally showed a higher obesity rate with high socioeconomic status, whereas women with low socioeconomic status tended to be more obese. The relationship between health behaviors and obesity did not differ significantly between genders, but men on a low-sodium diet were less obese while women on a low-sodium diet were more obese. Both men and women who responded that they did not walk as recommended, slept for lesser durations, and were severely stressed, had higher obesity rates.

These results are generally consistent with previous findings that lower socioeconomic status increases obesity. This is due to the intake of high-calorie and low-nutrition foods or environments that limit time and access to regular physical activities [14,15]. However, this relationship varies according to social environments and context. While lower socioeconomic status in developed countries is linked to higher risks of obesity, higher socioeconomic status in developing countries is associated with higher risks of obesity [16,17]. This is because with rapid growth in economy and technology in developing countries, food choices and daily consumption symbolize material wealth [18]. This study also showed that the socioeconomic status resulted in different way for obesity between men and women. As men’s social activities are traditionally more active than women South Korea, men with high socioeconomic status are more likely to engage in high-intensity labor, leading to be less time for regular physical activity or selecting healthy foods. However, women with high socioeconomic status might easily use the facilities for weight controls in their communities. It is necessary to explore lifestyles and cognitive factors in more detail to verify these findings.

The risk of obesity was low among those living in communities where residents have high socioeconomic status, are more satisfaction with safety and public transportation, and have high accessibility to sports facilities. These results are similar to previous studies reporting that environments with factors that encourage healthy lifestyles lead to low obesity rates. Frank et al. [19] analyzed the correlation between obesity and community environments related to walking, and reported that individuals living in communities with higher walkability had low obesity rates. Community characteristics, such as population density, density of residential areas, diversity of land use, convenience of public transportation, installation of bike paths, accessibility to relevant facilities, and walkability, were reported as factors that affect obesity [19,20].

Recently, there have been increased efforts in South Korea to examine the correlation between physical environmental factors and health in urban and regional planning and geography. A study by the Korea Research Institute for Human Settlements [21] examined the impacts of physical environmental factors on the health of urban dwellers in order to build a healthy city. They found that community environmental factors, such as green space, extension of bike paths, mixed land use, the number of fast food restaurants, and the number of beds in hospitals, significantly influenced community as well as individual obesity rates. Furthermore, a study by Lee et al. [22] on Seoul citizens reported that physical environments based on neighborhoods such as mixed land use, neighborhood parks, and accessibility to streams affected the pedestrian activities of residents.

However, studies examining the impacts of environmental factors on obesity typically focus on physical environment factors, mostly using the same indicators as previous studies of North America. Objective indicators of physical environment factors such as the number of sports facilities or parks may not sufficiently explain the relationship between environment and obesity or obesity-related health behaviors [23]. This suggests that when measuring the influence of environmental factors, objective indicators and the subjective perceptions about their environments may differ [24]. According to Gebel et al. [25], the walking rate is lower and the obesity rate is higher if individuals feel that the environment is not suitable for walking even when objective measures indicate otherwise.

Seoul is a city with high walkability due to a high density of residential areas and mixed land use, and public transportation is well developed as well [22]. However, physical activity is relatively low and a decreasing number of people report walking activity, while the obesity rate continues to grow. Thus, this study examined the relationship between obesity and perceived community environments measured by subjective variables. The results showed that subjective perceptions were more significantly correlated with obesity than objective indicators of physical environmental factors were. It is important to explore the contexts of perceptions and experiences, through which such community environmental factors may affect obesity prevention and management. Further studies using qualitative methods are called for.

CHS data analyzed in this study were derived from a cross-sectional survey and thus were limited in explaining their correlation with obesity. Moreover, since obesity was determined by BMI that were calculated by self-reported height and weight, the true obesity rates may have been underestimated. However, this study offers an in-depth analysis on the impacts of community environmental factors on obesity by using regional administrative data from various sources as well as subjective perceptions of individuals surveyed in the same communities.

To effectively prevent and manage obesity, it is necessary to develop strategies that consider the effects of diverse environmental factors of communities. Previous studies have shown that obesity prevention programs that consider both public policy and environmental factors were more successful [9,26,27]. The current obesity-related policies and programs in South Korea focus mostly on improving individual behaviors for prevention and management [28], but this individual-centered approach has been shown to be limited in its effectiveness [29]. This is because changing diet habits and physical activities, which is particularly important for obesity prevention and management, also requires changing environmental factors that affect these behaviors. It is also necessary to improve the social norms that emphasize individual efforts and responsibilities to prevent and manage obesity.

By exploring and highlighting community environments related to obesity based on a socioecological perspective, this study will provide a theoretical basis to emphasize social responsibility to deal with the obesity issues and support efforts to develop more effective intervention strategies for obesity prevention and management.