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Nursing and Health Sciences (2014), 16, 468–475
Research Article
Misperception of body weight and associated factors Sunjoo Boo, RN, PhD College of Nursing, Gachon University, Incheon, Korea
Abstract
The prevalence of obesity is increasing. In Korea, this is especially true of men in general, and women of low socioeconomic status. Misperception of body weight poses a barrier to the prevention of obesity. In this study, the misperception of body weight in relation to actual body weight and associated factors in Korean adults was evaluated. Data from 7162 adults who participated in the 2009 Korean National Health and Nutrition Examination Survey were analyzed. Misperception of body weight was substantial in Koreans, with 48.9% underestimating and 6.8% overestimating their weight status. More men than women underestimated their weight status. Weight perception in women was affected more by sociodemographic characteristics. Women’s underestimation was positively associated with older age, marital status, and lower socioeconomic status. This suggests that increasing public awareness of healthy weight will be helpful to counteract the current obesity epidemic in Korea.
Key words
body mass index, Korean, obesity, overweight, weight perception.
INTRODUCTION
Literature review
Obesity has become a major health concern worldwide, affecting both developed and developing countries (Yoon et al., 2006; Finucane et al., 2011; Boo & Froelicher, 2012). A recent study that analyzed 199 country data sets estimated that approximately 1.5 billion adults worldwide are either overweight or obese; of these, 500 million adults are obese, with a body mass index (BMI) of 30 or greater (Finucane et al., 2011). Although obesity trends and mean BMI are not uniform across countries, the worldwide obesity rate nearly doubled between 1980 and 2008. Furthermore, without urgent efforts to reverse the epidemic, it is estimated that an additional 500 million adults will be overweight or obese by 2030 (Kelly et al., 2008).Therefore, effective and well-targeted weight-loss interventions are crucial to tackle the global obesity challenge. In Korea, obesity has become a major public health concern, with rapid economic growth resulting in unhealthy changes in lifestyle and diet (Yoon et al., 2006; Boo & Froelicher, 2012).Trends in the prevalence of obesity in Korea vary by sex and socioeconomic status (SES) (Yoo et al., 2010). Between 1998 and 2007, obesity significantly increased in Korean men, while remaining stable in Korean women. A lower SES level is associated with a higher prevalence of obesity in Korean women, but not Korean men (Yoo et al., 2010). Such disparity in the prevalence of obesity might be partially influenced by weight perception, because dissatisfaction with weight is a strong predictor of trying to lose weight (Anderson et al., 2002; Lee et al., 2005; Lemon et al., 2009).
Weight perception is the subjective evaluation of one’s own body weight, and is related to weight-loss concerns or health-related behaviors (Clarke, 2002; Putterman & Linden, 2004). Studies conducted primarily in Western countries noted that weight perception is inadequately explained by actual body weight defined by BMI (Donath, 2000; Chang & Christakis, 2003; Wang et al., 2009). Men tend to underestimate, but women tend to overestimate their actual weight (Chang & Christakis, 2003; Lee et al., 2005; Wang et al., 2009). The relationships between SES and weight perception in previous studies are inconsistent (Chang & Christakis, 2003; Gregory et al., 2008; Bhanji et al., 2011). A study by Bhanji et al. (2011) found no significant association between weight perception and education level. Other studies showed that lower SES increases the chance of weight underestimation (Chang & Christakis, 2003; Gregory et al., 2008). However, the studies had weaknesses, in that they were conducted with limited samples (Lee et al., 2005; Bhanji et al., 2011), focused on a very narrow age range (Wang et al., 2009), or used self-reported weight and height to calculate BMI (Gregory et al., 2008). In addition, body weight perception is likely to be influenced by cultural factors, thus evidence from Western countries might not be applicable to Koreans. Furthermore, Asians, such as Koreans have a higher percentage of body fat and more centralized fat distribution compared to Caucasians of the same sex, age, and BMI, thus their risk of obesity-associated diseases is high, even at a lower BMI. Overweight and obesity for Asians are defined as a BMI ≥ 23 kg/m2 and BMI ≥ 25 kg/m2 (World Health Organization Asia–Pacific Region, 2000; World Health Organization Expert Consultation, 2004), lower than those for Western populations. Regrettably, many studies in Korea
Correspondence address: Sunjoo Boo, Ajou University, College of Nursing, oncheondong, Yeongtong-gu, Suwon, 443-721, South Korea. Email: [email protected] Received 21 November 2013; revision received 29 April 2014; accepted 4 May 2014 [Correction added on 10 September 2014, after first online publication: Corresponding author’s address and email address have been updated.]
© 2014 Wiley Publishing Asia Pty Ltd.
doi: 10.1111/nhs.12154
Misperception of body weight
use the cut-off points for Western populations to present the prevalence of obesity and problems related to obesity (Park et al., 2004; 2008; Yoon et al., 2006), which could lead to underestimation of the problem and a lack of public awareness. An accurate perception of weight is important, because as the health belief model suggests, individuals are more likely to take action to lose weight if they are aware that they are overweight or obese (Rosenstock et al., 1959; Becker & Maiman, 1975). Weight-loss interventions might have limited impact if there is a lack of correspondence between perceived weight status and actual body weight based on medical classifications. Given the rising obesity epidemic among Koreans, the purposes of this study were to evaluate the agreement, as well as the extent and type of discordance, between perceived body weight and actual body weight, and to investigate the independent effects of a broad range of sociodemographic factors on weight perception with a nationally-representative sample of Korean adults.
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weight or slightly underweight came under underweight for this study, thus the self-perceived weight status included the following four categories: underweight, approximately right, overweight, and obese. Covariates of interest were age, marital status, education level, poverty level, and work status. No official poverty line has been defined in Korea, so the concept of poverty income ratios (PIR) was used to define the poverty level for this study. The PIR represents the ratio of family income adjusted by family size to the poverty threshold, based on the minimum cost of living, as established by the Ministry of Health and Welfare (KRW 1,400,000/$US 1367.45 per month for a household of four people). Ratios below 1 indicate a family income below the poverty threshold, and were defined as being below the government poverty level in this study.
Data analysis
This was a cross-sectional study using data from the 2009 Korea National Health and Nutrition Examination Survey (KNHANES) (Korea Centers for Disease Control and Prevention, 2010). KNHANES is a cross-sectional national survey conducted to assess the health and nutritional status of Koreans using face-to-face interviews, self-administered questionnaires, and physical examinations. The response rate for the original survey was 79.2%. The sample for this study was limited to those who were aged ≥ 20 years and completed the survey. Women who were pregnant or breastfeeding were excluded, because pregnancy or lactation influences BMI and perceived weight status. Exclusions also included those with missing data on either BMI or perceived weight status. Of the 10,533 participants, 7356 were aged 20 years or older and completed the survey. Among them, 116 were pregnant or breastfeeding, and were therefore excluded. An additional 78 participants with missing data on either BMI or perceived weight status were excluded, yielding a final sample of 7162 participants (3138 men and 4024 women) for analysis.
Data management and statistical analyses were performed with SPSS Complex Samples 19.0 (SPSS, Chicago, IL, USA). All study variables were screened for missing data, outliners, and suspected errors. The KNHANES IV used a stratified, multistage probability sampling design, thus data were weighted to generate appropriate population estimates. Weighted means or percentages are presented to describe participant characteristics. Self-perceived weight status was compared with objective weight status with cross-tabulations separately by sex and sociodemographic characteristics. Based on the cross-tabulations, participants were placed into one of the following three categories: correspondence (selfperceived weight status agrees with the objective weight status), underestimation (self-evaluation is in lighter categories than objective weight status), and overestimation (selfevaluation is in heavier categories than objective weight status). Weighted kappa statistics with 95% confidence intervals were calculated to assess the level of agreement between self-perceived weight status and objective weight status. A kappa of 0.21–0.40 indicates fair agreement, 0.41–0.60 indicates moderate agreement, and indicates 0.61–0.80 substantial agreement (Viera & Garrett, 2005). Ordered logistic regressions were then used to assess the predictive effects of sociodemographic variables on self-perceived weight status as an ordered, four-category response variable.
Measures
Ethical considerations
BMI was calculated with measured height and weight (kg/ m2). The following BMI cut-off points were used for objective weight status classification in this study: underweight (BMI < 18.5 kg/m2), normal (18.5 ≤ BMI < 23 kg/m2), overweight (23 ≤ BMI < 25 kg/m2), and obese (BMI ≥ 25 kg/m2). These cut-off points are consistent with national and international public health directives for Koreans (World Health Organization Asia–Pacific Region, 2000; Korean Endocrine Society & Korean Society for the Study of Obesity, 2010). Self-perceived weight status was assessed by responses to the following survey question: “Do you consider yourself now to be very underweight, slightly underweight, approximately the right weight, overweight, or obese?” Very under-
The original survey was approved by the Korea Centers for Disease Control and Prevention Institutional Review Board (#01CON-03-2C). Informed consent was obtained from each KNHANES participant before data collection. This study used only de-identified existing data with no subject contact.
METHODS Design and participants
RESULTS Agreement between body weight perception and actual body weight status The participants’ characteristics are shown in Table 1. Crosstabulations of objective weight status by self-perceived © 2014 Wiley Publishing Asia Pty Ltd.
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Table 1.
S. Boo
Sample characteristics† (n = 7162) Men: 50.3% (0.6) (n = 3138)
Variables Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married and living together Education High school or above Less than high school Poverty level Above poverty Below poverty Body mass index Underweight Normal Overweight Obese Weight perception Thin Approximately the right weight Overweight Obese
Women: 49.7% (0.6) (n = 4024) Mean or % (SE)
Total
44.2 (0.4) 42.6 (1.4) 40.4 (1.3) 17.0 (0.8)
46.6 (0.4) 37.4 (1.3) 40.2 (1.1) 22.4 (1.0)
45.4 (0.4) 40.0 (1.2) 40.3 (1.0) 19.7 (0.8)
23.3 (1.2) 4.9 (0.5) 71.8 (1.3)
16.1 (1.0) 18.2 (0.9) 65.6 (1.1)
19.8 (0.9) 11.5 (0.6) 68.7 (1.0)
76.6 (1.0) 23.4 (1.0)
62.1 (1.2) 37.9 (1.2)
69.4 (1.0) 30.6 (1.0)
84.7 (0.9) 15.3 (0.9) 24.0 (0.1) 3.1 (0.4) 34.9 (1.1) 25.9 (0.9) 36.1 (1.0)
81.7 (1.0) 18.3 (1.0) 23.3 (0.1) 6.2 (0.5) 43.9 (1.0) 21.9 (0.8) 28.0 (0.9)
83.2 (0.8) 16.8 (0.8) 23.7 (0.1) 4.6 (0.3) 39.4 (0.7) 23.9 (0.6) 32.1 (0.7)
20.1 (0.9) 39.6 (1.1) 33.5 (1.1) 6.8 (0.6)
12.8 (0.6) 39.3 (0.9) 36.3 (0.8) 11.7 (0.6)
16.4 (0.5) 39.5 (0.8) 34.9 (0.7) 9.2 (0.4)
†Weighted using survey sampling weights. SE, standard error.
weight status are presented in Table 2. Overall, 44.3% of participants correctly perceived their own weight status. However, 55.7% misclassified, with 48.9% underestimating and 6.8% overestimating their weight status. Stratification of the cross-tabulation by sex revealed that men were more likely to underestimate their weight. Further stratification of the cross-tabulations by sociodemographic characteristics is presented in Table 3. How women view themselves was affected more by sociodemographic characteristics, with weighted kappa statistics ranging from 0.29 to 0.64. Agreement was especially substantial for women who were younger, never married, and of higher educational level (weighted kappa >0.60). However, agreement was fair for women who were older, married, of lower educational level, and of lower income. These women often underestimated their weight status. For men, weighted kappa statistics ranged from 0.29 to 0.45.
Variables associated with self-perceived weight status The results of the ordered logistic regression with selfperceived weight status are presented in Table 4. First, a nonstratified model showing a main effect for sex revealed that women, in contrast to men, were 3.6 times more likely to place themselves in a heavier weight perception category controlling for BMI and all the other covariates in the model. In both men and women, the young and middle-age groups had greater odds of placing themselves in a higher weight© 2014 Wiley Publishing Asia Pty Ltd.
perception category compared to the older age group, but the magnitude of the estimate was much greater in women. Marital status had no significant effect on weight perception for men, but for women, those who had never been married were 1.5 times more likely to place themselves in a heavier weight perception category compared to those married and living with a partner, controlling for BMI. Higher education, higher income, and enrollment significantly independently increased the odds of being in a higher weight-perception category in women.
DISCUSSION Obesity is a risk factor for many costly chronic diseases, such as diabetes mellitus and cardiovascular disease, which threaten individual lives, the stability of the healthcare system, and economies (Must et al., 1999). Given the significant burden of obesity, both personal and public, and the fact that weight loss can favorably reduce the risk for such diseases (Hamman et al., 2006; Pi-Sunyer et al., 2007), novel and well-targeted weight-loss interventions are urgently needed. Weight perception mediates the relationship between BMI and weight-loss efforts (Boo, 2013). Therefore, the results of this study have the potential to guide and inform effective and well-targeted weight-control interventions. This study clarifies two aspects of the misperception of body weight: underestimation and overestimation. Those who underestimate might not feel the need to lose weight,
29.4† 56.7 13.4‡ 0.5‡ 45.1† 51.6 3.1‡ 0.2‡ 19.5† 59.7 20.0‡ 0.8‡
86.2 13.5‡ 0.3‡ 0.0‡
94.6 4.5‡ 0.9‡ 0.0‡
81.8 18.2‡ 0.0‡ 0.0‡
5.7† 36.8† 52.9 4.6‡
4.1† 63.8† 31.0 1.1‡
5.0† 49.7† 42.4 2.9‡
2.7† 13.9† 49.9† 33.5
0.9† 17.9† 65.1† 16.1
1.9† 15.8† 57.2† 25.1
51.6
35.1
44.3
Agreement (%)
37.5
63.2
48.9
Underestimation(%)
10.9
1.7
6.8
Overestimation (%)
0.46
0.35
0.41
Weighted Kappa
(0.44, 0.48)
(0.33, 0.37)
(0.39, 0.42)
95% confidence interval
BMI, body mass index.
Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married Education Less than high school High school or over Poverty level Above poverty Below poverty Work status Yes No 59.3 67.3 62.4 56.7 65.2 64.6 62.0 63.8 63.6 61.5 64.5 59.5
41.0 33.7 34.0
36.0 34.6
35.0 35.8
33.9 38.6
Men Underestimation (%)
38.9 31.5 35.5
Correspondence (%)
1.6 1.9
1.4 2.7
1.9 1.5
2.5 1.2 1.4
1.8 1.3 2.0
Overestimation (%)
0.34 0.37
0.36 0.29
0.32 0.36
0.45 0.34 0.33
0.42 0.31 0.30
Weighted kappa
54.0 49.3
54.6 40.6
37.6 63.5
69.0 40.6 52.2
66.4 56.1 31.9
Correspondence (%)
34.7 40.3
33.0 53.5
57.9 20.1
6.5 54.8 37.3
12.3 34.3 65.9
11.3 10.4
12.2 5.9
4.5 16.4
24.4 4.8 10.5
21.3 9.7 2.2
Women Underestimation (%) Overestimation (%)
Agreement between body weight perception and actual body weight status based on measured BMI in Koreans by sociodemographic factors (n = 7162)
Characteristics
Table 3.
0.48 0.44
0.49 0.36
0.33 0.60
0.64 0.35 0.46
0.63 0.51 0.29
Weighted kappa
†Underestimation; ‡overestimation. Cell percentages are weighted using survey sampling weights; objective weight status: underweight (BMI < 18.5 kg/m2), normal (18.5 ≤ BMI < 23 kg/ m2), overweight (23 ≤ BMI < 25 kg/m2), and obesity (BMI ≥ 25 kg/m2). BMI, body mass index.
All (n = 7162) Underweight Approximately right Overweight Obese Men (n = 3138) Underweight Approximately right Overweight Obese Women (n = 4024) Underweight Approximately right Overweight Obese
Objective status based on BMI Underweight Normal Overweight Obese
Agreement between body weight perception and actual body weight status based on measured BMI in Koreans by sex (n = 7162)
Perceived weight
Table 2.
Misperception of body weight 471
© 2014 Wiley Publishing Asia Pty Ltd.
© 2014 Wiley Publishing Asia Pty Ltd. (0.7, 1.2) (0.8, 1.7) –
(0.8, 1.3) – (1.0, 1.6) – (0.8, 1.2) –
0.8 1.2 1.0
1.0 1.0
1.3* 1.0
1.0 1.0
1.2** 1.0
1.3** 1.0
1.7*** 1.0
1.5** 0.9 1.0
8.4*** 4.6*** 1.0
– –
2.2***
Odds ratio
(1.1, 1.4) –
(1.1, 1.5) –
(1.4, 2.0) –
(1.2, 1.9) (0.8, 1.1) –
(6.5, 10.9) (3.8, 5.6) –
– –
(2.1, 2.2)
Women 95% confidence interval
1.2* 1.0
1.3*** 1.0
1.5*** 1.0
1.4 0.7 1.0
3.7*** 2.5*** 1.0
3.6*** 1.0
2.2***
Odds ratio
(1.0, 1.3) –
(1.1, 1.5) –
(1.3, 1.7) –
(0.9, 1.2) (0.6, 0.8) –
(3.1, 4.5) (2.1, 2.8) –
(3.3, 4.1) –
(2.1, 2.2)
Total 95% confidence interval
*P < 0.05, **P < 0.01, ***P < 0.0001. Results of ordered logistic regression models of response to the question on self-perceived weight are shown. Odds ratios refer to the odds of being in a higher (heavier), rather than lower, weight-perception category, with “obese” as the highest category.
(1.2, 2.0) (1.0, 1.6) –
– –
(2.4, 2.6)
Men 95% confidence interval
1.6** 1.3* 1.0
– –
2.5***
Odds ratio
Variables associated with self-perceived weight status
Body mass index Sex Women Men Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married and living together Education High school or above Less than high school Poverty Above poverty Below poverty Work status Yes No
Variables
Table 4.
472 S. Boo
Misperception of body weight
and therefore, could be at risk of obesity-related health problems. However, those who overestimate might have unnecessary weight concerns, and therefore, could be at risk of excessive dieting. The two aspects of misperception certainly have different implications, and therefore, evaluating the extent and type of discordance between perceived body weight and actual weight status should be the first step in planning weight-control interventions. By contrasting actual weight and perceived weight status separately by sociodemographic factors with a national sample of Koreans, the findings of this study can be helpful in deciding where to direct weight-control interventions, as well as in designing more appropriate interventions for each misperception. This study showed that misperception of weight status is widespread among Koreans. Weighted kappa was 0.41, indicating moderate agreement. Sex showed significant large effects on the misperception of weight status. The agreement between objective and subjective weight was fair in men (weighted kappa 0.35) and lower than in women (weighted kappa 0.46). Underestimation was much more common than overestimation, with 48.9% underestimating and 6.8% overestimating their weight status. Men were more likely than women to underestimate their weight. Controlling for BMI and other covariates, women had 3.6 times greater odds of viewing themselves as overweight (Table 4). Almost 68% of overweight men and 84% of obese men underestimated their own weight status, compared to 43% of overweight women and 67% of obese women. This sex difference in weight perception has been reported in several different settings (Donath, 2000; Gregory et al., 2008; Wang et al., 2009; Bhanji et al., 2011). A study conducted with a national sample of Australians found that approximately one in two men and one in four women thought they weighed less than they really did (Donath, 2000). Gregory et al. (2008) reported on a public sample of US adults that 26.5% of men and approximately 7% of women failed to perceive themselves to be overweight or obese. Perceptions of being of normal weight among overweight individuals is a critical problem, because the underestimation of weight in overweight individuals is significantly related to a lower likelihood of weight-control behaviors (Lee et al., 2005; Kim et al., 2008; Wang et al., 2009), but carries a high risk of obesity-related health problems, such as cardiovascular disease. While the general tendency of underestimating weight in Koreans is consistent with research in other settings, the proportions of underestimation in Koreans found in this study are much higher than those in other studies. One explanation might be in part due to the lower BMI cut-off points for overweight and obesity used in this study. Koreans might look thinner than Caucasians, so they might not consider themselves overweight. Koreans might lack knowledge about ideal weight, so they might not accurately perceive their risk for overweight or obesity. Lack of awareness of healthy weight can be a barrier to accurate weight perception and weight-loss efforts (Bhanji et al., 2011). Koreans need to be better informed regarding the definition of healthy body weight. The underestimation of body weight in adults can also be a serious issue, because their misperception affects how they view their child’s body size. Evidence shows that a child’s risk
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of obesity greatly increases if one or more parent is overweight or obese (Jelastopulu et al., 2012). More importantly, parents who are overweight or obese tend to underestimate their child’s excess weight (Doolen et al., 2009). If parents are in denial about their child’s size, they are unlikely encourage their son or daughter to lose weight. Given that overweight or obese children are more likely to remain that way into adulthood, parents’ accurate perceptions of their body weight can be pivotal in preventing childhood obesity and reversing the current obesity epidemic. While underestimation is widespread among Koreans, overestimation can also be a critical problem. Overestimation of weight, independent of BMI, is related to increased use of undesirable weight-control behaviors, such as skipping meals or taking laxatives (Kim et al., 2008). In this study, women accounted for the most overestimation. Women who were younger, had never married, had a higher educational level, and had a higher income were especially likely to overestimate their own weight status. However, women who were older, married, had a lower educational level, and had a lower income often underestimated their own weight status (Table 4). In contrast, such sociodemographic disparities in weight perception, were not obvious in men; the prevalence of underestimation remained substantial, even among men in the youngest group (59.3%), those who had never married (56.7%), had a higher education (63.8%), and had a higher income (63.6%) (Table 3). The relationship between sociodemographic status and body weight perception in the literature is mixed. Chang and Christakis (2003) found that older age, lower income, and lower education each significantly and independently related with weight underestimation in both men and women, but marital status was not a significant determinant of weight perception, even among women. In a study by Gregory et al. (2008), age did not affect body weight perception, and lower education was only significantly associated with women’s weight perception. Kuchler and Variyam (2003) reported that approximately 40% of women in any subgroups of age less than 65 years overestimated their weight status. These inconsistent findings can be explained by local social and cultural factors that influence body weight norms and attitudes toward body size. In the traditional Korean culture when food was scarce, being overweight was considered a symbol of health and wealth (Holdsworth et al., 2004; Fernald, 2009). Given the recent and rapid economic development and urbanization in Korea, food is readily available, and as such, people’s preferences have shifted toward thinner body shapes, especially in young women. Thinness among women is considered important for feminine beauty or physical attractiveness, and helps with marriageability. Overweight young women are considered to have poor self-control, but attitudes toward men are more lenient (Jung & Forbes, 2006; Jung & Forbes, 2007). In this study, the majority of young, unmarried women viewed themselves as overweight, while the majority of overweight men did not see themselves as such. This suggests that most men still adhere to the traditional Korean cultural ideal of being overweight as a symbol of health and wealth. In addition, the older women are, the more likely they are to underestimate their weight, suggesting a generational shift in body © 2014 Wiley Publishing Asia Pty Ltd.
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weight norms. An alternative possibility is that as overweight and obesity become more common with advancing age (Boo & Froelicher, 2012), women’s attitudes toward ideal weight might change as they age. A trend in the same direction was noted for men, but the magnitude was much smaller. Furthermore, the fact that higher education and higher income each significantly independently increase the odds of placing oneself in a heavier weight-perception category among women suggests that women evaluate their own weight status largely with reference to their peer group. There might be norms of acceptable range for body size depending on age and SES. This study has several limitations that must be acknowledged. First, the use of BMI as a measure of actual body weight does not take into account body fat and body fat distribution. Body fat and its distribution, and the ratio of muscle versus fat mass might be more associated with obesity-related diseases, as well as body weight perception than BMI. Second, body weight perception is a multidimensional concept that captures several elements. The KNHANES provides a single assessment of weight perception; further studies with a stronger assessment of perceived weight, such as body size satisfaction, could produce different results. However, the greatest strengths of this study are the use of a nationally-representative sample of Koreans, wellestablished methods and procedures, a high response rate, and the use of ethnically-specific BMI cut-off points appropriate for Koreans. Because SES (as measured by a variety of indicators) is associated with weight status in populationbased and clinical research across cultures and regions, the inclusion of SES as a key variable is also viewed as a strength. In addition, data were weighted to incorporate sampling designs into the analyses. Therefore, this study produces reliable population-level estimates, thus the results of this study can be especially useful for public health planning.
Conclusion The results of this study found that weight perception significantly varies by sex and SES in Korean adults after adjustment for BMI. Given that weight perception is related to health behaviors associated with weight status, the results of this study have the potential to guide and inform sex- and SES-specific interventions focused on optimal weight for Korean adults. Overall, weight underestimation was substantial in Korean adults. More men than women underestimated their weight status. Women’s underestimation was positively associated with older age and lower SES. In contrast, the relationship was not as obvious in men. Interestingly, the risks of weight underestimation found in this study are consistent with the sociodemographic disparities in the prevalence of obesity in Korea. The prevalence of obesity is increasing, especially in men and in women with low SES (Yoo et al., 2010).This suggests that weight misperception poses a barrier to the treatment and prevention of obesity in Korea. Healthcare providers need to understand that cultural, as well as sociodemographic, factors influence the body weight norms and attitudes toward body size. When promoting lifestyle changes to counteract obesity epidemics, the potential © 2014 Wiley Publishing Asia Pty Ltd.
S. Boo
target should be increasing public awareness of ideal weight. The sex and SES differences in weight perception suggest the need for intervention programs specifically tailored to target audiences. Providing ideal weight ranges for each height can be an effective way to foster accurate weight perception and assist in setting appropriate weight goals, especially for those who misperceive their weight. Further studies are warranted to evaluate whether changes in weight perception via educational nursing interventions lead to actual weight-loss behaviors, whether efforts to lose weight involve desirable or undesirable ways, and whether the relationship between body weight perception and weight-loss behaviors differs by sociodemographic disparities. In addition, because obesity is a global issue, slowing down increases in obesity and reversing the epidemic will require multifaceted, large-scale efforts within individual countries, as well as across the globe.
ACKNOWLEDGMENT This study was supported by Gachon University research fund of 2013 (GCU-2013-M032).
CONTRIBUTIONS Study Design: SB. Data Collection and Analysis: SB. Manuscript writing: SB.
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Misperception of body weight
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Nursing and Health Sciences (2014), 16, 468–475
Research Article
Misperception of body weight and associated factors Sunjoo Boo, RN, PhD College of Nursing, Gachon University, Incheon, Korea
Abstract
The prevalence of obesity is increasing. In Korea, this is especially true of men in general, and women of low socioeconomic status. Misperception of body weight poses a barrier to the prevention of obesity. In this study, the misperception of body weight in relation to actual body weight and associated factors in Korean adults was evaluated. Data from 7162 adults who participated in the 2009 Korean National Health and Nutrition Examination Survey were analyzed. Misperception of body weight was substantial in Koreans, with 48.9% underestimating and 6.8% overestimating their weight status. More men than women underestimated their weight status. Weight perception in women was affected more by sociodemographic characteristics. Women’s underestimation was positively associated with older age, marital status, and lower socioeconomic status. This suggests that increasing public awareness of healthy weight will be helpful to counteract the current obesity epidemic in Korea.
Key words
body mass index, Korean, obesity, overweight, weight perception.
INTRODUCTION
Literature review
Obesity has become a major health concern worldwide, affecting both developed and developing countries (Yoon et al., 2006; Finucane et al., 2011; Boo & Froelicher, 2012). A recent study that analyzed 199 country data sets estimated that approximately 1.5 billion adults worldwide are either overweight or obese; of these, 500 million adults are obese, with a body mass index (BMI) of 30 or greater (Finucane et al., 2011). Although obesity trends and mean BMI are not uniform across countries, the worldwide obesity rate nearly doubled between 1980 and 2008. Furthermore, without urgent efforts to reverse the epidemic, it is estimated that an additional 500 million adults will be overweight or obese by 2030 (Kelly et al., 2008).Therefore, effective and well-targeted weight-loss interventions are crucial to tackle the global obesity challenge. In Korea, obesity has become a major public health concern, with rapid economic growth resulting in unhealthy changes in lifestyle and diet (Yoon et al., 2006; Boo & Froelicher, 2012).Trends in the prevalence of obesity in Korea vary by sex and socioeconomic status (SES) (Yoo et al., 2010). Between 1998 and 2007, obesity significantly increased in Korean men, while remaining stable in Korean women. A lower SES level is associated with a higher prevalence of obesity in Korean women, but not Korean men (Yoo et al., 2010). Such disparity in the prevalence of obesity might be partially influenced by weight perception, because dissatisfaction with weight is a strong predictor of trying to lose weight (Anderson et al., 2002; Lee et al., 2005; Lemon et al., 2009).
Weight perception is the subjective evaluation of one’s own body weight, and is related to weight-loss concerns or health-related behaviors (Clarke, 2002; Putterman & Linden, 2004). Studies conducted primarily in Western countries noted that weight perception is inadequately explained by actual body weight defined by BMI (Donath, 2000; Chang & Christakis, 2003; Wang et al., 2009). Men tend to underestimate, but women tend to overestimate their actual weight (Chang & Christakis, 2003; Lee et al., 2005; Wang et al., 2009). The relationships between SES and weight perception in previous studies are inconsistent (Chang & Christakis, 2003; Gregory et al., 2008; Bhanji et al., 2011). A study by Bhanji et al. (2011) found no significant association between weight perception and education level. Other studies showed that lower SES increases the chance of weight underestimation (Chang & Christakis, 2003; Gregory et al., 2008). However, the studies had weaknesses, in that they were conducted with limited samples (Lee et al., 2005; Bhanji et al., 2011), focused on a very narrow age range (Wang et al., 2009), or used self-reported weight and height to calculate BMI (Gregory et al., 2008). In addition, body weight perception is likely to be influenced by cultural factors, thus evidence from Western countries might not be applicable to Koreans. Furthermore, Asians, such as Koreans have a higher percentage of body fat and more centralized fat distribution compared to Caucasians of the same sex, age, and BMI, thus their risk of obesity-associated diseases is high, even at a lower BMI. Overweight and obesity for Asians are defined as a BMI ≥ 23 kg/m2 and BMI ≥ 25 kg/m2 (World Health Organization Asia–Pacific Region, 2000; World Health Organization Expert Consultation, 2004), lower than those for Western populations. Regrettably, many studies in Korea
Correspondence address: Sunjoo Boo, Ajou University, College of Nursing, oncheondong, Yeongtong-gu, Suwon, 443-721, South Korea. Email: [email protected] Received 21 November 2013; revision received 29 April 2014; accepted 4 May 2014 [Correction added on 10 September 2014, after first online publication: Corresponding author’s address and email address have been updated.]
© 2014 Wiley Publishing Asia Pty Ltd.
doi: 10.1111/nhs.12154
Misperception of body weight
use the cut-off points for Western populations to present the prevalence of obesity and problems related to obesity (Park et al., 2004; 2008; Yoon et al., 2006), which could lead to underestimation of the problem and a lack of public awareness. An accurate perception of weight is important, because as the health belief model suggests, individuals are more likely to take action to lose weight if they are aware that they are overweight or obese (Rosenstock et al., 1959; Becker & Maiman, 1975). Weight-loss interventions might have limited impact if there is a lack of correspondence between perceived weight status and actual body weight based on medical classifications. Given the rising obesity epidemic among Koreans, the purposes of this study were to evaluate the agreement, as well as the extent and type of discordance, between perceived body weight and actual body weight, and to investigate the independent effects of a broad range of sociodemographic factors on weight perception with a nationally-representative sample of Korean adults.
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weight or slightly underweight came under underweight for this study, thus the self-perceived weight status included the following four categories: underweight, approximately right, overweight, and obese. Covariates of interest were age, marital status, education level, poverty level, and work status. No official poverty line has been defined in Korea, so the concept of poverty income ratios (PIR) was used to define the poverty level for this study. The PIR represents the ratio of family income adjusted by family size to the poverty threshold, based on the minimum cost of living, as established by the Ministry of Health and Welfare (KRW 1,400,000/$US 1367.45 per month for a household of four people). Ratios below 1 indicate a family income below the poverty threshold, and were defined as being below the government poverty level in this study.
Data analysis
This was a cross-sectional study using data from the 2009 Korea National Health and Nutrition Examination Survey (KNHANES) (Korea Centers for Disease Control and Prevention, 2010). KNHANES is a cross-sectional national survey conducted to assess the health and nutritional status of Koreans using face-to-face interviews, self-administered questionnaires, and physical examinations. The response rate for the original survey was 79.2%. The sample for this study was limited to those who were aged ≥ 20 years and completed the survey. Women who were pregnant or breastfeeding were excluded, because pregnancy or lactation influences BMI and perceived weight status. Exclusions also included those with missing data on either BMI or perceived weight status. Of the 10,533 participants, 7356 were aged 20 years or older and completed the survey. Among them, 116 were pregnant or breastfeeding, and were therefore excluded. An additional 78 participants with missing data on either BMI or perceived weight status were excluded, yielding a final sample of 7162 participants (3138 men and 4024 women) for analysis.
Data management and statistical analyses were performed with SPSS Complex Samples 19.0 (SPSS, Chicago, IL, USA). All study variables were screened for missing data, outliners, and suspected errors. The KNHANES IV used a stratified, multistage probability sampling design, thus data were weighted to generate appropriate population estimates. Weighted means or percentages are presented to describe participant characteristics. Self-perceived weight status was compared with objective weight status with cross-tabulations separately by sex and sociodemographic characteristics. Based on the cross-tabulations, participants were placed into one of the following three categories: correspondence (selfperceived weight status agrees with the objective weight status), underestimation (self-evaluation is in lighter categories than objective weight status), and overestimation (selfevaluation is in heavier categories than objective weight status). Weighted kappa statistics with 95% confidence intervals were calculated to assess the level of agreement between self-perceived weight status and objective weight status. A kappa of 0.21–0.40 indicates fair agreement, 0.41–0.60 indicates moderate agreement, and indicates 0.61–0.80 substantial agreement (Viera & Garrett, 2005). Ordered logistic regressions were then used to assess the predictive effects of sociodemographic variables on self-perceived weight status as an ordered, four-category response variable.
Measures
Ethical considerations
BMI was calculated with measured height and weight (kg/ m2). The following BMI cut-off points were used for objective weight status classification in this study: underweight (BMI < 18.5 kg/m2), normal (18.5 ≤ BMI < 23 kg/m2), overweight (23 ≤ BMI < 25 kg/m2), and obese (BMI ≥ 25 kg/m2). These cut-off points are consistent with national and international public health directives for Koreans (World Health Organization Asia–Pacific Region, 2000; Korean Endocrine Society & Korean Society for the Study of Obesity, 2010). Self-perceived weight status was assessed by responses to the following survey question: “Do you consider yourself now to be very underweight, slightly underweight, approximately the right weight, overweight, or obese?” Very under-
The original survey was approved by the Korea Centers for Disease Control and Prevention Institutional Review Board (#01CON-03-2C). Informed consent was obtained from each KNHANES participant before data collection. This study used only de-identified existing data with no subject contact.
METHODS Design and participants
RESULTS Agreement between body weight perception and actual body weight status The participants’ characteristics are shown in Table 1. Crosstabulations of objective weight status by self-perceived © 2014 Wiley Publishing Asia Pty Ltd.
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Table 1.
S. Boo
Sample characteristics† (n = 7162) Men: 50.3% (0.6) (n = 3138)
Variables Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married and living together Education High school or above Less than high school Poverty level Above poverty Below poverty Body mass index Underweight Normal Overweight Obese Weight perception Thin Approximately the right weight Overweight Obese
Women: 49.7% (0.6) (n = 4024) Mean or % (SE)
Total
44.2 (0.4) 42.6 (1.4) 40.4 (1.3) 17.0 (0.8)
46.6 (0.4) 37.4 (1.3) 40.2 (1.1) 22.4 (1.0)
45.4 (0.4) 40.0 (1.2) 40.3 (1.0) 19.7 (0.8)
23.3 (1.2) 4.9 (0.5) 71.8 (1.3)
16.1 (1.0) 18.2 (0.9) 65.6 (1.1)
19.8 (0.9) 11.5 (0.6) 68.7 (1.0)
76.6 (1.0) 23.4 (1.0)
62.1 (1.2) 37.9 (1.2)
69.4 (1.0) 30.6 (1.0)
84.7 (0.9) 15.3 (0.9) 24.0 (0.1) 3.1 (0.4) 34.9 (1.1) 25.9 (0.9) 36.1 (1.0)
81.7 (1.0) 18.3 (1.0) 23.3 (0.1) 6.2 (0.5) 43.9 (1.0) 21.9 (0.8) 28.0 (0.9)
83.2 (0.8) 16.8 (0.8) 23.7 (0.1) 4.6 (0.3) 39.4 (0.7) 23.9 (0.6) 32.1 (0.7)
20.1 (0.9) 39.6 (1.1) 33.5 (1.1) 6.8 (0.6)
12.8 (0.6) 39.3 (0.9) 36.3 (0.8) 11.7 (0.6)
16.4 (0.5) 39.5 (0.8) 34.9 (0.7) 9.2 (0.4)
†Weighted using survey sampling weights. SE, standard error.
weight status are presented in Table 2. Overall, 44.3% of participants correctly perceived their own weight status. However, 55.7% misclassified, with 48.9% underestimating and 6.8% overestimating their weight status. Stratification of the cross-tabulation by sex revealed that men were more likely to underestimate their weight. Further stratification of the cross-tabulations by sociodemographic characteristics is presented in Table 3. How women view themselves was affected more by sociodemographic characteristics, with weighted kappa statistics ranging from 0.29 to 0.64. Agreement was especially substantial for women who were younger, never married, and of higher educational level (weighted kappa >0.60). However, agreement was fair for women who were older, married, of lower educational level, and of lower income. These women often underestimated their weight status. For men, weighted kappa statistics ranged from 0.29 to 0.45.
Variables associated with self-perceived weight status The results of the ordered logistic regression with selfperceived weight status are presented in Table 4. First, a nonstratified model showing a main effect for sex revealed that women, in contrast to men, were 3.6 times more likely to place themselves in a heavier weight perception category controlling for BMI and all the other covariates in the model. In both men and women, the young and middle-age groups had greater odds of placing themselves in a higher weight© 2014 Wiley Publishing Asia Pty Ltd.
perception category compared to the older age group, but the magnitude of the estimate was much greater in women. Marital status had no significant effect on weight perception for men, but for women, those who had never been married were 1.5 times more likely to place themselves in a heavier weight perception category compared to those married and living with a partner, controlling for BMI. Higher education, higher income, and enrollment significantly independently increased the odds of being in a higher weight-perception category in women.
DISCUSSION Obesity is a risk factor for many costly chronic diseases, such as diabetes mellitus and cardiovascular disease, which threaten individual lives, the stability of the healthcare system, and economies (Must et al., 1999). Given the significant burden of obesity, both personal and public, and the fact that weight loss can favorably reduce the risk for such diseases (Hamman et al., 2006; Pi-Sunyer et al., 2007), novel and well-targeted weight-loss interventions are urgently needed. Weight perception mediates the relationship between BMI and weight-loss efforts (Boo, 2013). Therefore, the results of this study have the potential to guide and inform effective and well-targeted weight-control interventions. This study clarifies two aspects of the misperception of body weight: underestimation and overestimation. Those who underestimate might not feel the need to lose weight,
29.4† 56.7 13.4‡ 0.5‡ 45.1† 51.6 3.1‡ 0.2‡ 19.5† 59.7 20.0‡ 0.8‡
86.2 13.5‡ 0.3‡ 0.0‡
94.6 4.5‡ 0.9‡ 0.0‡
81.8 18.2‡ 0.0‡ 0.0‡
5.7† 36.8† 52.9 4.6‡
4.1† 63.8† 31.0 1.1‡
5.0† 49.7† 42.4 2.9‡
2.7† 13.9† 49.9† 33.5
0.9† 17.9† 65.1† 16.1
1.9† 15.8† 57.2† 25.1
51.6
35.1
44.3
Agreement (%)
37.5
63.2
48.9
Underestimation(%)
10.9
1.7
6.8
Overestimation (%)
0.46
0.35
0.41
Weighted Kappa
(0.44, 0.48)
(0.33, 0.37)
(0.39, 0.42)
95% confidence interval
BMI, body mass index.
Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married Education Less than high school High school or over Poverty level Above poverty Below poverty Work status Yes No 59.3 67.3 62.4 56.7 65.2 64.6 62.0 63.8 63.6 61.5 64.5 59.5
41.0 33.7 34.0
36.0 34.6
35.0 35.8
33.9 38.6
Men Underestimation (%)
38.9 31.5 35.5
Correspondence (%)
1.6 1.9
1.4 2.7
1.9 1.5
2.5 1.2 1.4
1.8 1.3 2.0
Overestimation (%)
0.34 0.37
0.36 0.29
0.32 0.36
0.45 0.34 0.33
0.42 0.31 0.30
Weighted kappa
54.0 49.3
54.6 40.6
37.6 63.5
69.0 40.6 52.2
66.4 56.1 31.9
Correspondence (%)
34.7 40.3
33.0 53.5
57.9 20.1
6.5 54.8 37.3
12.3 34.3 65.9
11.3 10.4
12.2 5.9
4.5 16.4
24.4 4.8 10.5
21.3 9.7 2.2
Women Underestimation (%) Overestimation (%)
Agreement between body weight perception and actual body weight status based on measured BMI in Koreans by sociodemographic factors (n = 7162)
Characteristics
Table 3.
0.48 0.44
0.49 0.36
0.33 0.60
0.64 0.35 0.46
0.63 0.51 0.29
Weighted kappa
†Underestimation; ‡overestimation. Cell percentages are weighted using survey sampling weights; objective weight status: underweight (BMI < 18.5 kg/m2), normal (18.5 ≤ BMI < 23 kg/ m2), overweight (23 ≤ BMI < 25 kg/m2), and obesity (BMI ≥ 25 kg/m2). BMI, body mass index.
All (n = 7162) Underweight Approximately right Overweight Obese Men (n = 3138) Underweight Approximately right Overweight Obese Women (n = 4024) Underweight Approximately right Overweight Obese
Objective status based on BMI Underweight Normal Overweight Obese
Agreement between body weight perception and actual body weight status based on measured BMI in Koreans by sex (n = 7162)
Perceived weight
Table 2.
Misperception of body weight 471
© 2014 Wiley Publishing Asia Pty Ltd.
© 2014 Wiley Publishing Asia Pty Ltd. (0.7, 1.2) (0.8, 1.7) –
(0.8, 1.3) – (1.0, 1.6) – (0.8, 1.2) –
0.8 1.2 1.0
1.0 1.0
1.3* 1.0
1.0 1.0
1.2** 1.0
1.3** 1.0
1.7*** 1.0
1.5** 0.9 1.0
8.4*** 4.6*** 1.0
– –
2.2***
Odds ratio
(1.1, 1.4) –
(1.1, 1.5) –
(1.4, 2.0) –
(1.2, 1.9) (0.8, 1.1) –
(6.5, 10.9) (3.8, 5.6) –
– –
(2.1, 2.2)
Women 95% confidence interval
1.2* 1.0
1.3*** 1.0
1.5*** 1.0
1.4 0.7 1.0
3.7*** 2.5*** 1.0
3.6*** 1.0
2.2***
Odds ratio
(1.0, 1.3) –
(1.1, 1.5) –
(1.3, 1.7) –
(0.9, 1.2) (0.6, 0.8) –
(3.1, 4.5) (2.1, 2.8) –
(3.3, 4.1) –
(2.1, 2.2)
Total 95% confidence interval
*P < 0.05, **P < 0.01, ***P < 0.0001. Results of ordered logistic regression models of response to the question on self-perceived weight are shown. Odds ratios refer to the odds of being in a higher (heavier), rather than lower, weight-perception category, with “obese” as the highest category.
(1.2, 2.0) (1.0, 1.6) –
– –
(2.4, 2.6)
Men 95% confidence interval
1.6** 1.3* 1.0
– –
2.5***
Odds ratio
Variables associated with self-perceived weight status
Body mass index Sex Women Men Age (years) 20–39 40–59 ≥60 Marital status Never married Formerly married Married and living together Education High school or above Less than high school Poverty Above poverty Below poverty Work status Yes No
Variables
Table 4.
472 S. Boo
Misperception of body weight
and therefore, could be at risk of obesity-related health problems. However, those who overestimate might have unnecessary weight concerns, and therefore, could be at risk of excessive dieting. The two aspects of misperception certainly have different implications, and therefore, evaluating the extent and type of discordance between perceived body weight and actual weight status should be the first step in planning weight-control interventions. By contrasting actual weight and perceived weight status separately by sociodemographic factors with a national sample of Koreans, the findings of this study can be helpful in deciding where to direct weight-control interventions, as well as in designing more appropriate interventions for each misperception. This study showed that misperception of weight status is widespread among Koreans. Weighted kappa was 0.41, indicating moderate agreement. Sex showed significant large effects on the misperception of weight status. The agreement between objective and subjective weight was fair in men (weighted kappa 0.35) and lower than in women (weighted kappa 0.46). Underestimation was much more common than overestimation, with 48.9% underestimating and 6.8% overestimating their weight status. Men were more likely than women to underestimate their weight. Controlling for BMI and other covariates, women had 3.6 times greater odds of viewing themselves as overweight (Table 4). Almost 68% of overweight men and 84% of obese men underestimated their own weight status, compared to 43% of overweight women and 67% of obese women. This sex difference in weight perception has been reported in several different settings (Donath, 2000; Gregory et al., 2008; Wang et al., 2009; Bhanji et al., 2011). A study conducted with a national sample of Australians found that approximately one in two men and one in four women thought they weighed less than they really did (Donath, 2000). Gregory et al. (2008) reported on a public sample of US adults that 26.5% of men and approximately 7% of women failed to perceive themselves to be overweight or obese. Perceptions of being of normal weight among overweight individuals is a critical problem, because the underestimation of weight in overweight individuals is significantly related to a lower likelihood of weight-control behaviors (Lee et al., 2005; Kim et al., 2008; Wang et al., 2009), but carries a high risk of obesity-related health problems, such as cardiovascular disease. While the general tendency of underestimating weight in Koreans is consistent with research in other settings, the proportions of underestimation in Koreans found in this study are much higher than those in other studies. One explanation might be in part due to the lower BMI cut-off points for overweight and obesity used in this study. Koreans might look thinner than Caucasians, so they might not consider themselves overweight. Koreans might lack knowledge about ideal weight, so they might not accurately perceive their risk for overweight or obesity. Lack of awareness of healthy weight can be a barrier to accurate weight perception and weight-loss efforts (Bhanji et al., 2011). Koreans need to be better informed regarding the definition of healthy body weight. The underestimation of body weight in adults can also be a serious issue, because their misperception affects how they view their child’s body size. Evidence shows that a child’s risk
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of obesity greatly increases if one or more parent is overweight or obese (Jelastopulu et al., 2012). More importantly, parents who are overweight or obese tend to underestimate their child’s excess weight (Doolen et al., 2009). If parents are in denial about their child’s size, they are unlikely encourage their son or daughter to lose weight. Given that overweight or obese children are more likely to remain that way into adulthood, parents’ accurate perceptions of their body weight can be pivotal in preventing childhood obesity and reversing the current obesity epidemic. While underestimation is widespread among Koreans, overestimation can also be a critical problem. Overestimation of weight, independent of BMI, is related to increased use of undesirable weight-control behaviors, such as skipping meals or taking laxatives (Kim et al., 2008). In this study, women accounted for the most overestimation. Women who were younger, had never married, had a higher educational level, and had a higher income were especially likely to overestimate their own weight status. However, women who were older, married, had a lower educational level, and had a lower income often underestimated their own weight status (Table 4). In contrast, such sociodemographic disparities in weight perception, were not obvious in men; the prevalence of underestimation remained substantial, even among men in the youngest group (59.3%), those who had never married (56.7%), had a higher education (63.8%), and had a higher income (63.6%) (Table 3). The relationship between sociodemographic status and body weight perception in the literature is mixed. Chang and Christakis (2003) found that older age, lower income, and lower education each significantly and independently related with weight underestimation in both men and women, but marital status was not a significant determinant of weight perception, even among women. In a study by Gregory et al. (2008), age did not affect body weight perception, and lower education was only significantly associated with women’s weight perception. Kuchler and Variyam (2003) reported that approximately 40% of women in any subgroups of age less than 65 years overestimated their weight status. These inconsistent findings can be explained by local social and cultural factors that influence body weight norms and attitudes toward body size. In the traditional Korean culture when food was scarce, being overweight was considered a symbol of health and wealth (Holdsworth et al., 2004; Fernald, 2009). Given the recent and rapid economic development and urbanization in Korea, food is readily available, and as such, people’s preferences have shifted toward thinner body shapes, especially in young women. Thinness among women is considered important for feminine beauty or physical attractiveness, and helps with marriageability. Overweight young women are considered to have poor self-control, but attitudes toward men are more lenient (Jung & Forbes, 2006; Jung & Forbes, 2007). In this study, the majority of young, unmarried women viewed themselves as overweight, while the majority of overweight men did not see themselves as such. This suggests that most men still adhere to the traditional Korean cultural ideal of being overweight as a symbol of health and wealth. In addition, the older women are, the more likely they are to underestimate their weight, suggesting a generational shift in body © 2014 Wiley Publishing Asia Pty Ltd.
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weight norms. An alternative possibility is that as overweight and obesity become more common with advancing age (Boo & Froelicher, 2012), women’s attitudes toward ideal weight might change as they age. A trend in the same direction was noted for men, but the magnitude was much smaller. Furthermore, the fact that higher education and higher income each significantly independently increase the odds of placing oneself in a heavier weight-perception category among women suggests that women evaluate their own weight status largely with reference to their peer group. There might be norms of acceptable range for body size depending on age and SES. This study has several limitations that must be acknowledged. First, the use of BMI as a measure of actual body weight does not take into account body fat and body fat distribution. Body fat and its distribution, and the ratio of muscle versus fat mass might be more associated with obesity-related diseases, as well as body weight perception than BMI. Second, body weight perception is a multidimensional concept that captures several elements. The KNHANES provides a single assessment of weight perception; further studies with a stronger assessment of perceived weight, such as body size satisfaction, could produce different results. However, the greatest strengths of this study are the use of a nationally-representative sample of Koreans, wellestablished methods and procedures, a high response rate, and the use of ethnically-specific BMI cut-off points appropriate for Koreans. Because SES (as measured by a variety of indicators) is associated with weight status in populationbased and clinical research across cultures and regions, the inclusion of SES as a key variable is also viewed as a strength. In addition, data were weighted to incorporate sampling designs into the analyses. Therefore, this study produces reliable population-level estimates, thus the results of this study can be especially useful for public health planning.
Conclusion The results of this study found that weight perception significantly varies by sex and SES in Korean adults after adjustment for BMI. Given that weight perception is related to health behaviors associated with weight status, the results of this study have the potential to guide and inform sex- and SES-specific interventions focused on optimal weight for Korean adults. Overall, weight underestimation was substantial in Korean adults. More men than women underestimated their weight status. Women’s underestimation was positively associated with older age and lower SES. In contrast, the relationship was not as obvious in men. Interestingly, the risks of weight underestimation found in this study are consistent with the sociodemographic disparities in the prevalence of obesity in Korea. The prevalence of obesity is increasing, especially in men and in women with low SES (Yoo et al., 2010).This suggests that weight misperception poses a barrier to the treatment and prevention of obesity in Korea. Healthcare providers need to understand that cultural, as well as sociodemographic, factors influence the body weight norms and attitudes toward body size. When promoting lifestyle changes to counteract obesity epidemics, the potential © 2014 Wiley Publishing Asia Pty Ltd.
S. Boo
target should be increasing public awareness of ideal weight. The sex and SES differences in weight perception suggest the need for intervention programs specifically tailored to target audiences. Providing ideal weight ranges for each height can be an effective way to foster accurate weight perception and assist in setting appropriate weight goals, especially for those who misperceive their weight. Further studies are warranted to evaluate whether changes in weight perception via educational nursing interventions lead to actual weight-loss behaviors, whether efforts to lose weight involve desirable or undesirable ways, and whether the relationship between body weight perception and weight-loss behaviors differs by sociodemographic disparities. In addition, because obesity is a global issue, slowing down increases in obesity and reversing the epidemic will require multifaceted, large-scale efforts within individual countries, as well as across the globe.
ACKNOWLEDGMENT This study was supported by Gachon University research fund of 2013 (GCU-2013-M032).
CONTRIBUTIONS Study Design: SB. Data Collection and Analysis: SB. Manuscript writing: SB.
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