Slender women and overweight men: gender differences in the educational gradient in body weight in South Korea

Obesity has become increasingly prevalent in countries where it was rarely a problem in the past. Several factors account for this, including these countries experiencing remarkable economic growth, and the emergence of an obesogenic environment [1, 2]. The emergence of obesogenic environments makes the human agency and knowledge that accrue from schooling more important for obesity prevention as people are exposed to fast changes in physical activity patterns and dietary intake [3].

Obesity is typically more prevalent among women because women’s bodies are adapted to store more fat due to biological factors related to reproduction [4]. The experience of childbirth also significantly increases the probability of obesity [5]. Recent studies have documented that the gender differences in being overweight and obesity prevalence vary by social and cultural contexts, which indicates that gender is an important social factor of obesity as well as a biological marker [6, 7].

Research from Western countries links higher education with a lower risk of obesity but whether the shape and strength of the relationship varies by gender is inconclusive [8]. Relatively less is known about the gender-specific mechanisms through which education is associated with weight status in non-Western societies that have experienced a rapid rise in their obesity rates. Men and women are exposed to higher education in different ways and gain unequal socioeconomic returns to their levels of education in the societies with a rigid gender hierarchy [9, 10]. Furthermore, there are potential gender differences in social consequences of obesity [11], and in the cultural ideologies regarding body shape [12], which contribute to generating different motivation for men and women to manage the emerged obesogenic environments.

Higher levels of education enable people to be more efficient in health production, for example, more educated people may be better able to practice an efficient allocation of caloric intake and expenditure [13, 14]. The effect of education is indirectly attributable to economic resources that may protect them against risk factors for obesity. Education is also closely associated with cultural capital and predisposes people to be knowledgeable about normative codes of desirable physical appearance [15]. Therefore, the variation in the educational gradients in weight status among men and women may be reflective of gender-linked differences in normative cultural codes regarding ideal body size. Social pressure to conform to ideal body shape may vary between men and women [16]. In developed societies, obese individuals are often stigmatized and social penalties for being obese are greater for women than for men [17]. The culture that conveys ubiquitous images of female celebrities with thin bodies also encourages people to consider slimness as part of feminine beauty and as a characteristic of social distinction [18, 19]. Women are more sensitive to their body shape particularly in anti-egalitarian countries where they are more likely to be evaluated by societal conventions based on physical appearance than men. In these societies, women’s beauty is more likely to be valued as a symbolic asset, e.g., a beauty premium, which translates into tangible social resources in the labor and marriage market [20, 21].

South Korea (hereafter ‘Korea’) has experienced a rapid economic development. State-led industrialization has led to an enormous occupational transition from rural primary product sectors to service and manufacturing sectors, which have contributed to reduced physical activity [22]. Access to high-calorie foods became easier and cheaper through the growth of convenience food stores and restaurants [23]. Due to fast social change, most Korean adults who spent early childhood without knowledge of obesity are now facing an obesity epidemic.

Even if the prevalence of obesity in Korea is relatively moderate compared to other high- and middle-income countries (<30% according to Yoon et al., 2006), it has been growing quickly, especially among middle-aged men [1]. The statistics from the Korean National Health Survey showed that the prevalence of people whose Body Mass Index (BMI) is over 25 kg/m² significantly increased over the last two decades from 13.9% in 1995 to 31.5% in 2014. Although much slower increase in obesity has been observed among women in Korea [24] severe educational disparities in weight status have been observed for women in recent years [25]. According to the cross-national statistics among the 11 Organisation for Economic Co-operation and Development (OECD) countries, the largest educational differences in being overweight and obesity have been observed for Korean women along with Spanish women, while the smallest educational inequalities have been found for Korean men [26]. Despite the stark gender differences in educational gradients in weight status, little is known about what creates the variations between men and women in this society.

Despite the expansion of higher education, which has reduced the gender gap in educational attainment, gender inequalities in labor force participation, wages, and type of employment remain substantial in Korea. According to the “glass-ceiling index” of the Economist (2016) based on the latest cross-national data, Korea is the worst place to be a working woman among 30 OECD countries. Korea has the largest gender wage gap and Korean women are least likely to be in senior managerial positions, which is far behind women in Scandinavian countries [27]. Most Korean women do not obtain the same level of economic rewards and autonomy as men of a similar level of education. The report issued by the Korea Statistical Information Service (KOSIS) in 2016 showed that only about 53% of working-aged Korean women (aged 15 and older) participate in the labor force, compared to 74.7% of men [28]. Thus, it is possible that for women the effect of education may not be attributable to economic resources and play a direct role in determining health and health behaviors. Furthermore, studies have documented significant barriers in the Korean labor market that contribute to the interruption of occupational careers of women upon marriage and childbearing [9]. In the context of a strong gender division of labor, men’s earnings may be a particularly crucial factor in marriage markets and a married woman’s social status is likely to be determined by her husband’s social status [29]. Therefore, women’s bodies are often sexually objectified by men in the process of mate selection, which may drive women toward investing in human capital to achieve physical attractiveness [30, 31]. On the other hand, better educated Korean men are less likely to be under appearance-related social pressures and less likely to be sensitive to body size [32].

Health-related lifestyles are sometimes at odds with the ideology of the groups or organizations that people belong to [33]. Individuals are expected to conform to the group’s dominant ideology in order to avoid any possible disadvantages from not fulfilling the normative rules [34]. Collective practices in Korea support the norm favoring longer working hours. The 2014 OECD statistics show that Korea has the longest working hours compared to other high income countries [35]. Long working hours decrease workers’ time for outdoor activities and sleep which play a significant role in the etiology of obesity [36]. Korean male workers are also under pressure to participate in drinking gatherings as an extension of formal working hours to improve work place relations [37]. Embedded in a cultural system of social interactions, alcohol consumption, a ‘social lubricant’, is positively perceived by professional and sales workers as a way to show solidarity with one’s business network and to ease the stress associated with work [38]. Heavy drinking falls into a line of masculine icons in Asian culture while it places a taboo on women who drink [39]. Unhealthy behaviors such as sitting behind a desk all day, overworking while reducing leisure time, and binge drinking have been supported as a virtue shared by elite groups that measure social success among Korean men of working age. This may lead Korean men with college educations, who are generally more likely to have sedentary jobs and higher incomes than men with low levels of education, to be exposed to higher behavioral risks for gaining weight [40]. Thus, education may not be a strong predictor of being overweight and obesity among Korean men after controlling for economic resources, for whom behaviors promoting healthy weight often conflict with a collective ideology at work [38], and for whom motivation to obtain professional success is stronger than a desire for better appearance.

Using repetitive cross-sectional data from 2008 to 2012, this study extends previous literature by examining how the link between education and body weight distribution operates before and after controlling for other socioeconomic characteristics and health behaviors within the structure of gender relations in Korea. We also hypothesize that Korean men are more likely to under-estimate their body weight compared to Korean women and the educational gradient in weight perception will be less pronounced among men than women. We investigate whether Korean women with higher educational attainment are more likely to perceive their body weight as being higher than their actual weight status and women with lower educational attainment perceive their weight as being lower than their actual weight status.

To examine gender differences in the distribution of the explanatory variables, t-tests were used for quantitative variables and chi-square tests were used for categorical variables. Conditional quantile regression model was adopted to estimate the effect of education on the entire distribution of BMI, not merely on its conditional mean. The quantile regression method focuses on the educational gradients in both the right and the left tail of the BMI distributions known to be related with high health risks [45]. For instance, the education gradient may be steeper at the right tail of the BMI distributions, which indicates that higher education offers greater protection against weight gain in overweight groups. This approach also properly deals with nonlinearities in the relationships of BMI with its predictors. We assessed whether the coefficients of education vary at high versus low quantiles of body weight and how they change before and after controlling for potential mediators. Current study adopted a bootstrap method to estimate standard errors with 100 replications. All models were estimated separately for men and women. Model 1 evaluates the bivariate relationship between educational attainment and BMI. Model 2 includes demographic characteristics (e.g., age, year of survey, marital status, and region of residence) and income and occupation as plausible economic mediators. In model 3, health behaviors are added to model 2 to examine whether behavioral mediators further explain the associations between education, economic and occupational status, and BMI. Model 2 and 3 also control for parental education and self-rated health, which may affect respondents’ educational attainment and health behaviors, and reflect family backgrounds. We performed sensitivity analyses that compared alternative way of coding the BMI variable. Using multinomial logit regressions, we assessed the associations between BMI categories, educational attainment, and the hypothesized pathway variables. The models compared underweight, overweight, and obese categories relative to the reference category of normal weight.

Second, to see whether there are educational gradients in weight perception among men and women, the analysis regressed weight perception on age, year of survey, education, BMI categories (underweight, normal, overweight, obesity), and interaction terms between education and the BMI categories. The estimates were weighted by survey weights to be nationally representative and account for the complex sampling design of KNHANES. The study produced predicted probabilities of whether people perceive themselves as having “average” weight using the results of the multinomial logit regressions. The mean difference in the predicted probabilities of perceiving body image as average was compared by educational attainment and BMI categories for women and men while setting all other covariates at their means. All models were estimated in Stata 12.

Previous studies documented that the shape and strength of the relationship between education and weight are not always homogeneous across demographic groups within a country [2, 4, 5]. Extending previous findings, the current study demonstrates clear gender differences in the way education is related to body weight and weight perception. Korean men who have higher educational attainment are more likely to gain weight across the entire BMI distribution than men who have lower educational attainment but the relationship is reversed among women. Given that the positive relationship between education and obesity is not common in contemporary developed countries these clear gender differences in Korean society are interesting [6] Unlike women, highly educated men appeared to be heavier and the relationship was mostly explained by economic resources, particularly occupational status. Among men, behaviors among high-status workers are not consistent with a healthy lifestyle [34] and more highly educated men may thus not be socially motivated to engage in healthy behaviors [34, 46]. Korean culture encourages long working hours, e.g., the early bird catches the worm, and sedentary lifestyles are common in higher status occupations, e.g., high-ranking officials have private drivers etc. In addition, Korean men traditionally tend to place a high value on socializing, while viewing drinking positively as a crucial component to building masculine social networks [47]. Our finding that heavy drinking and long working hours tend to have a larger impact on men at the higher quantile of BMI supports that health behaviors play a crucial role in well-off men’s obesity status in particular.

Another possible explanation is that highly educated Korean women tend to be more sensitive to their body shape compared to men counterparts. Considering that Korean women have fewer opportunities for transferring educational attainment into economic resources than men due to the gender hierarchy, and women’s social status would be determined by their husband’s economic status, women may utilize their human capital to obtain symbolic resources such as physical attractiveness. Well-educated Korean women are more likely to accrue prestige by setting themselves apart with weight-related behaviors reflected by the boom in the fitness and plastic surgery industries in this country [48]. Education increases the demand for dieting although highly educated women have a lower objective “need,” but less educated women do not have the cultural means to afford special diets and are less likely to be motivated to override emerging obesogenic environments [49]. The finding shows that overweight women with lower educational attainment are likely to under-estimate their body size and this tendency is consistent across different age groups. These factors contribute to generating stronger educational inequalities in the ‘ideal slim look’ among Korean women compared to other developed countries. The social standards of gender roles may influence the ways men and women allocate their time to various activities during the day such that men with college educations are likely to spend more time at paid work, relative to women with college educations who are less likely to be in the labor market [50]. In a gendered society where the price of time use for non-paid work is much greater for men than women, men may have time constraints and spend less of their time engaged in leisure activities as a main breadwinner, particularly when they are working in higher-status jobs. In this condition, highly educated men are more likely to be exposed to obesity risk factors. Koreans also appear to have less aversion regarding large body size for men and tend to be less judgmental about men’s physical appearance [49]. Discrimination based on appearance in the labor and marriage market is relatively mild for men as compared to women. As we can see in Figs. 1 and 2, men were more likely to under-perceive their body size than women, that is, overweight men tend to consider themselves to be of ‘average’ weight, regardless of their educational attainment.

One of the main limitations of the study is the lack of longitudinal data on individuals’ body weight and body perception trajectories. Therefore, we cannot derive further inference about the causal effect of educational attainment on changes in weight status or weight control behaviors. It is also possible that the correlation between educational attainment and body weight and weight perceptions are derived from unobserved factors affecting both educational attainment and weight status. Future studies also need to consider gender differences in other important behavioral mediators, such as calorie intake, social capital, and psychological status, which were not included in current study due to the lack of reliable data.

The current study examined the association between educational attainment and weight status, whether the association operated mainly through attained economic resources and health behaviors, and how these mechanisms varied by gender. Although education may help maintain a healthy weight in Western countries, it may not always be a protective factor in societies with different cultures. This research shed light on the intersection of gender and human capital that explains gender differences in health and health behaviors in context with structural gender-inequalities. It encourages future research on the nature of education as an important factor that helps people override unhealthy lifestyles in rapidly developing societies, especially those that have strong gender hierarchy.