The moderating effect of gender on the relationships between obesity, well-being, and stress perception in Korean adolescents

Childhood obesity has been identified as one of the major public health problems in the United States and many industrialized countries of the world [1, 2]. In Korea, the obesity rate among children and adolescents is increasing every year. As of 2018, the obesity rate of 13–18 years old was 14.4% [3]. The association of obesity with morbid outcomes makes it a public health concern for children and adolescents [4]. In addition, research indicates that children with obesity are much more likely to suffer from cardiovascular and digestive diseases in adulthood [5]. An increase in body fat also exposes an adolescent to an increased risk of numerous forms of cancer, such as breast, colon, esophageal, kidney, and pancreatic cancers [6]. Therefore, obesity prevention in adolescence is essential for eliminating the complications associated with obesity that can affect health throughout the lifespan [7].

Furthermore, studies have demonstrated that, in addition to its impact on physical health, obesity increases the risk of mental illnesses such as depression [8], with a direct relationship having been found between the two [9]. These studies, which focused on the relationship between obesity and health, suggest that, as the level of obesity increases, physical and mental health decline, and as the degree of dissatisfaction with one’s body type increases, the quality of life decreases [10] and disease morbidity increases [7]. Numerous studies have analyzed the relationship between obesity and the prevalence of morbidity, mortality, and quality of life; however, most of these studies have focused on obesity based on the body mass index (BMI), (OBB), and not on obesity based on perception (OBP). OBP refers to the perception of one’s body type as underweight, healthy weight, overweight, or obese, regardless of one’s BMI. Empirical studies have suggested that there is a discrepancy between OBB and OBP [11, 12]. One previous study found a considerable discrepancy between OBB and OBP, with women more likely than men. and younger adults more likely than middle-aged people to overestimate their OBB [13].

Overall, however, studies on the relationship between obesity and psychological problems have shown contradictory results. Some studies have suggested that if adolescents perceived themselves as obese, then their levels of anxiety and stress increase, their level of depression increases, and they have lower self-esteem [14, 15]. In one study, adolescents with obesity based on BMI were more likely to have psychological problems [16], but another study found no significant relationship between the likelihood of psychological problems and OBB [17]. To clarify the relationship between obesity and psychological problems, recent studies have utilized measures of OBP rather than OBB [18].

Adolescents are interested in body shape and appearance and compare their body shape to that of their peers, which suggests that obesity in adolescence not only is a health problem but may also negatively affect emotional development. In adolescence, a distorted self-perception of body shape is a risk factor for psychological problems and inappropriate methods of weight control [19]. In particular, excessive weight control and poor eating habits due to distorted body perception and body dissatisfaction have been found in girls [20]. Overall, girls were found to be less satisfied with their weight and body shape than boys [21]. Previous studies on Chinese [22], American [23], and European [24] women reported that they overestimated their weight by 21.02, 23.50, and 23.80%, respectively; in all cases, the proportion of women overestimating their weight was higher than that of men. Although their BMIs were appropriate, the women reported utilizing various methods to lose weight [25]. This finding suggests that women are more affected by the perception of being thin, consistent with its emphasis in the media as the ideal body image [26]. Distorted body perception is related to body dissatisfaction and attempting unhealthy weight control strategies, which lead to body dysmorphic disorder, health-obsessive behaviors, low quality of life, and eating disorders [27‐29]. Also, distorted body perception and weight control strategies are related to the prevalence of psychological problems, as people with inaccurate perceptions of their body shape who use medical procedures for weight control could be at a higher risk of psychological disorders [30].

The disparity between OBB and OBP varies by gender. For example, an empirical study reported that 38.3% of girls with healthy weight subjectively perceived themselves to be overweight, while 32.8% of overweight boys perceived themselves to be underweight or having a healthy weight [31]. The relationship between self-esteem and the disparity between OBB and OBP may also vary by gender. One study found that the more girls perceived themselves as underweight rather than having a healthy weight or obese, the higher their self-esteem; however, the more boys perceive themselves as underweight rather than obese, the lower their self-esteem [18]. Overall, an inaccurate or distorted perception of one’s body negatively affected both girls and boys.

Therefore, this study examines the effects of OBB and OBP on the well-being and stress perception of adolescents and whether the relationship between them is moderated by gender. To this end, the main and interaction effects of OBB, OBP, and gender are investigated. To clarify the relationship between obesity and psychological problems in adolescents, the study poses the following research questions: (1) What are the main effects of OBB and OBP on well-being and stress perception? (2) Is gender a moderator in the relation of OBB or OBP with well-being and stress perception?

Using the 2019 KAHB, this study examined the effects of OBB and OBP on well-being and stress perception and the moderating effect of gender on the relationship between them among Korean adolescents. In adolescence, the perception of one’s body type may be distorted due to the influence of mass media, and this distorted perception of body type may cause psychological problems and serve as a risk factor for inappropriate methods of weight control [19]. Previous research has suggested that a distorted perception of body type and indiscriminate weight control due to body dissatisfaction are more frequently found in females than in males [20], which is consistent with the results of this study. In this study, there was no significant difference in OBB between males and females. However, for OBP, the ratio of males in the group with underweight was higher than that for females, and in the group with obesity, the proportion of females was higher than that for males. These results are consistent with those of a previous study, in which researchers found that men were more likely than women to perceive their body shape correctly, with women tending to overestimate their OBB [36]. Similarly, in a study of middle and high school adolescents, gender was one of the strongest predictors of high school students’ perceptions of obesity [37]. Additional research has reported that female adolescents perceived their weight more negatively than male adolescents, were more interested in appearances than males, and perceived themselves as more obese than males [38, 39]. In addition, women were more likely to mistakenly perceive their bodies as obese because they compared themselves to the ideal thin body type delivered through mass media [40].

The results of the general linear model indicated that well-being and stress perception are influenced by OBP rather than OBB, and this influence varies according to gender. Well-being scores were the highest for both males and females with a healthy weight. For females, there was no significant difference in well-being between the group with underweight and the group with healthy weight; however, for males, the score of the group with underweight was lower than that of the group with healthy weight. Especially for females, the well-being scores for the group with obesity were significantly lower than for that the other groups. These results are consistent with those of a previous study, which reported that males who perceived themselves as underweight had low body satisfaction and self-esteem [18], and women who overestimated their weight reported the most negative psychological conditions including anxiety, self-esteem, body satisfaction, quality of life, and eating attitudes [30]. However, although the interaction effect between OBP and gender on stress perception was statistically significant, both men and women showed very similar results for stress perception; the scores were highest for the group with obesity and decreased in order for the groups with underweight and healthy weight.

In this study, the interaction effects of OBP and gender on well-being and stress perception were found to be statistically significant, but their effect sizes were small, at 0.02 and 0.03. In particular, because the results for stress perception were similar for women and men, it is difficult to completely exclude the possibility that the only valid main effects were those for OBP and gender. However, when interaction effects are present, it suggests that interpretation of the main effects is incomplete or misleading [41‐43]. Therefore, it is necessary to consider an interaction effect, even if its effect size is small. In addition, many previous studies have reported a strong relationship between gender and body perception [19, 22, 23, 44, 45] and the importance of gender in relation to the mental health of people with a distorted perception of body weight [46, 47]. For example, one study found that overestimated OBB was positively correlated with depressive symptoms among women [48]. Another study with an adolescent sample, conducted in China demonstrated that girls were more likely than boys to have an overestimated body perception and higher levels of depression and anxiety [49].

Furthermore, the rapid growth and development of the adolescent body increases perceptual interest in the body and requires adolescents to revise their perception of body type, making precise recognition of the adolescent body one of the most important developmental tasks. Therefore, it is expected that an accurate body perception is essential for the healthy development of adolescents, and an effective plan for their dietary management and exercise can be established if OBP matches OBB. Accordingly, education and strategy development are needed to help teenagers accurately recognize the adolescent body.

OBB and OBP coincided in 51.5% of the sample. However, the degree of obesity was overestimated and underestimated by 29.4 and 19.0% of the sample, respectively. In addition, OBB and OBP were found to vary by gender, age, economic status, and academic achievement.

The main effect of OBB was not statistically significant, but the main effects of OBP and the interaction effect of OBP and gender on well-being and stress perception were all statistically significant. Well-being scores were higher for males than females, and the scores for the group with perceptual obesity were the lowest. There was no difference in well-being scores between females who perceived themselves as underweight and those who perceived themselves as having a healthy weight, but the scores of men who perceived themselves as underweight were higher than those of men who perceived themselves as having a healthy weight. For stress perception, females scored higher than males. Also, both males and females who perceived themselves as obese had the highest stress perception scores. The well-being and stress perception are influenced by obesity based on perception rather than obesity based on BMI, and this influence varies according to gender in adolescents.