Journal of Obesity & Metabolic Syndrome

Search

Article

J Obes Metab Syndr 2022; 31(4): 313-324

Published online December 30, 2022 https://doi.org/10.7570/jomes22051

Copyright © Korean Society for the Study of Obesity.

Self-perceived Weight and Mortality in Korean Adults Based on the Korea National Health and Nutrition Examination Survey Data Linked to Cause of Death Statistics

Kayoung Lee *

Department of Family Medicine, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea

Correspondence to:
Kayoung Lee
https://orcid.org/0000-0002-2816-554X
Department of Family Medicine, Busan Paik Hospital, Inje University College of Medicine, 75 Bokji-ro, Busanjin-gu, Busan 47392, Korea
Tel: +82-51-890-6229
Fax: +82-51-894-7554
E-mail: kayoung.fmlky@gmail.com

Received: August 30, 2022; Reviewed : November 1, 2022; Accepted: December 10, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background: This study aimed to determine the associations between self-perceived weight, weight perception, and mortality risk among Korean adults.
Methods: Data from the 2007 to 2015 Korea National Health and Nutrition Examination Survey and the 2007 to 2019 Cause of Death Statistics were linked for this cohort study. A complex samples Cox regression analysis involving 42,453 participants (17,056 male; 25,397 female) was performed after excluding those who died within 1 year of the follow-up period, those with a history of cancer, those with cardiovascular diseases, those without body mass index (BMI) data, and those without self-perceived weight data.
Results: During 7.85 years of follow-up, the overall mortality rate was 3.8% (4.5% for male and 3.1% for female). Self-perceived thin weight status was associated with a 43% to 68% higher risk of all-cause mortality and a 2.48-times higher risk of cardiovascular mortality compared to self-perceived just right weight status after controlling for sociodemographic characteristics, health-related behaviors, underlying health status, BMI, and metabolic syndrome. After adjusting for the confounding factors, those who underestimated their weight had a 27% reduced risk of all-cause mortality than those who correctly estimated their weight. The risks of all-cause mortality and cardiovascular mortality were 2.14-times higher and 2.32-times higher, respectively, in the underweight group with an accurate weight estimation than in the normal weight group with an accurate weight estimation. However, all-cause mortality was 47% lower among participants with obesity who overestimated their weight.
Conclusion: Self-perceived thinness and accurately perceived underweight status were associated with increased risks of all-cause mortality and cardiovascular mortality among Korean adults.

Keywords: Self concept, Weight perception, Mortality

Recent cross-sectional studies have indicated that subjectively perceived weight status is related to self-rated health and health-related quality of life. Perceptions of self as underweight or overweight have been linked to greater odds of suboptimal self-rated health and general life satisfaction, independent of body mass index (BMI), by the Canadian Community Health Survey (n=87,545 adults; age, 18–65 years).1 During a study of young adults 24 to 34 years of age (n=7,044 female; n=6,594 male), independent of BMI, those who thought they were overweight or underweight reported having worse health than those who thought their weight was normal.2 According to data from the Korea National Health and Nutrition Examination Survey (KNHANES; n=43,883 adults; age 19 years or older), participants who underestimated or overestimated their weight were more likely to have a poor health-related quality of life than those who accurately perceived their weight.3 During another study based on the KNHANES data (n=8,397 male, n=11,211 female; age, 40–80 years), individuals who accurately estimated their underweight status regardless of sex or age and those who correctly identified themselves as obese during middle age were most likely to have poorer self-rated health.4

The self-perceived weight status can be affected by subjectively perceived weight discrimination. Self-perceived weight discrimination has been associated with physical issues such as obesity, chronic infections, and an increased burden of chronic diseases, as well as mental health issues such as stress and dementia.5,6 It has also been linked to unhealthy lifestyles and an increased mortality risk.5 Considering the association between subjectively perceived weight and self-rated health, which was independent of actual weight;2 the relationship between self-rated health and mortality risk,7,8 and the relationship between weight discrimination and mortality risk,5 it can be hypothesized that self-perceived weight may be associated with mortality risk, and that this relationship may be independent of actual weight. However, self-perceived weight and weight perception have been associated with long-term weight gain. Among overweight or obese teenagers, the underestimated weight assessment group gained less weight than the accurate weight assessment group, and self-perceived obesity increased the risk of obesity after 12 years.9,10 A systematic review study also indicated that individuals who perceive their weight status as overweight are more likely to report trying to lose weight but eventually gaining more weight.11 Considering the relationship between weight gain and high mortality risk,12 a relationship between weight perception and mortality risk can be assumed.

The associations between self-perceived weight, weight perception, and mortality risk have not received as much attention as the relationship between BMI and the risk of death, which has been the topic of several studies.13-16 Evidence of long-term health issues associated with self-perceived weight and weight perception can be found by examining the relationships between self-perceived weight, weight perception, and the risk of death, independent of the measured weight status and whether it has been considered. Therefore, this study aimed to evaluate the relationships between self-perceived weight, weight perception, and mortality risk among Korean adults using the KNHANES data linked to the Cause of Death Statistics.

Study participants

The KNHANES evaluates the health and health-related behaviors of the Korean population and serves as the foundation for developing and assessing health policies. Furthermore, it includes a health interview, health examination survey, and nutrition survey. The KNHANES data were gathered using a rolling sampling design that involved a complex, stratified, and multistage probability cluster survey.17 Consent was obtained from the KNHANES participants since 2007 by linking with the following data: Statistics Korea’s Death Statistics; the Korea Central Cancer Registry of the National Cancer Center; Claims Data of the National Health Insurance Service; and Health Insurance Review and Assessment Service. Based on the data from 2020, statistics regarding the cause of death and related data were constructed and disclosed to researchers. Data obtained by linking the 2007 to 2015 KNHANES data with the 2007 to 2019 Cause of Death Statistics are currently available (dataset version 1.2).18,19

Of the 53,101 individuals 19 years of age or older who participated in the 2007 to 2015 KNHANES health examination survey, 51,575 who agreed to link their data and had valid registration numbers were included in the linked dataset. However, 3,426 of the 51,575 individuals comprising the linked dataset died between 2007 and 2019 during an average follow-up of 8.4 years according to the cutoff date of December 31, 2019.19

Among them, those who died within 1 year of the follow-up period (n=93), those with a history of cancer (stomach cancer, liver cancer, colon cancer, breast cancer, cervical cancer, lung cancer, or thyroid cancer; n=823), those with cardiovascular diseases (stroke or ischemic heart disease; n=556), those who did not have BMI data (n=218), and those who did not have self-perceived body shape data (n=1,854) were excluded from this study. Therefore, 42,453 participants (17,056 male; 25,397 female) were included in the study after the exclusion criteria were applied.

The KNHANES is in agreement with the guidelines of the Declaration of Helsinki. The Institutional Review Board of the Korean Centers for Disease Control and Prevention approved all procedures involving human subjects. All participants provided written informed consent. The Institutional Review Board of Busan Paik Hospital Inje University approved the study protocol (No. 2022-04-045).

Weight-related parameters

Trained study assistants performed weight and height measurements. BMI was computed by dividing the weight in kilograms by the height in meters squared. According to the 2018 Korean Society for the Study of Obesity Guideline for Management of Obesity, BMI was classified as follows: underweight, 18.5 kg/m2; normal weight, 18.5 to <23.0 kg/m2; overweight, 23.0 to <25.0 kg/m2; and obesity, ≥25.0 kg/m2.20 During the self-administered surveys, five categories of self-perceived weight were evaluated. Participants were asked the following: “What do you think about your current body shape?”; the five options for answering this question were “very thin,” “thin,” “just right,” “slightly fat,” and “very fat.”21

Subsequently, the BMI-based weight categorization and self-perceived weight classification were compared, and weight perception was categorized. Self-perceived “very thin” was regarded as underweight because the prevalence of underweight according to BMI and that of self-perceived “very thin” were comparable (4.5% and 4.6%, respectively). Therefore, these five self-perceived weights were reclassified as “very thin” (underweight), “thin,” “just right” (normal weight), “slightly fat” (overweight), and “very fat” (obesity) to denote weight perception. If the BMI-based and self-perceived weight classifications coincided, then the perception was considered accurate. If the self-perceived weight category was lower than the BMI-based weight category, then the perception was defined as an underestimation. Overestimation was defined as a self-perceived weight category exceeding the BMI-based weight category.1-4

Cause of death statistics

The causes of death comprising the linked data were based on the subcategories of the Korean Standard Classification of Diseases (7th revision). The cause of death and the year and month when death occurred were related to the death statistics.19 All-cause mortality, cardiovascular disease mortality (I05-I99), and cancer mortality (C02-D47) were the endpoints of the analyses.

Covariates

The following factors were investigated using questionnaires and interviews: economic status; educational background; marital status; presence of chronic diseases (yes or no for hypertension, dyslipidemia, diabetes mellitus, pulmonary tuberculosis, renal failure, depression, and liver cirrhosis); self-rated health status; depressive mood (yes or no for depression for ≥2 consecutive weeks); and health-related behaviors. Health-related behaviors included monthly drinking (yes or no for ≥1 drink/mo over the course of the past year), smoking status (current, former, or non-smoker), physical activity (yes or no for aerobic physical activity, which comprised ≥2 hours and 30 minutes of moderate-intensity exercise, ≥1 hour and 15 minutes of high-intensity exercise, a combination of high-intensity and moderate-intensity physical activity [1 minute of high-intensity exercise corresponds to 2 minutes of moderate-intensity exercise], or walking [≥30 min/session and ≥5 day/wk]).

Waist circumference was measured to the nearest 0.1 cm at the end of normal expiration at the midpoint between the lowest rib and iliac crest. Blood pressure was measured three times using a standard manual sphygmomanometer while the participants were seated. The average of the second and third blood pressure measurements was used for the analyses. Antecubital venous blood samples were collected from each subject after a 12-hour overnight fast. An automatic analyzer (Automatic Chemistry Analyzer 7600; Hitachi, Tokyo, Japan) was used to measure high-density lipoprotein cholesterol and triglyceride levels using an enzyme method and glucose levels using calorimetry. Metabolic syndrome was defined when at least three of the following characteristics were present: waist circumference ≥90 cm (for male) or 85 cm (for female);19,21,22 blood pressure ≥130/85 mmHg or a history of hypertension; fasting plasma glucose level ≥5.6 mmol/L or a history of diabetes mellitus; high-density lipoprotein cholesterol level <1.03 mmol/L for male or 1.29 mmol/L for female; and triglyceride level ≥1.7 mmol/L.23 Using a standardized questionnaire, an individual was defined as having a history of hypertension or diabetes mellitus based on the diagnosis determined by a physician or the current use of treatment for these illnesses.24

Statistical analysis

Sampling weights and a complex survey design (clusters and strata) were considered during all analyses.17,25 The Rao-Scott modified chi-square test was used to determine the relationships of weight-related indicators and confounding factors for survival and death. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality, cancer mortality, and cardiovascular mortality according to self-perceived weight, weight perception, and combinations of BMI categories and weight perception. The follow-up durations for all participants were computed using the time from their participation year and month to their death year and month in the case of the deceased; in the case of survivors, they were computed using the time from their participation year and month to December 2019. During cancer or cardiovascular mortality analyses, those who died from other causes were censored along with the survivors, and only death attributable to the cause was considered an outcome event, assuming that those who were censored had the same disease-specific mortality. A test of the proportional hazards assumption was performed to compare the fitted model to an alternative model that included time-dependent predictors for each predictor using the Kaplan-Meier time function. When P<0.05 was observed during the test for model assumptions, HRs and 95% CIs using an alternative model were adopted.

Sociodemographic characteristics, health-related behaviors, self-rated health, depression, and chronic disease status were adjusted in the analyses using Cox proportional hazards models. The BMI (only for analysis of self-perceived weight) and metabolic syndrome were further adjusted. In these models, the interactions between sex and self-perceived weight-related indicators were analyzed; then, sex-specific HRs and 95% CIs for all-cause mortality according to self-perceived weight-related indicators were assessed. Data were analyzed using the IBM SPSS software ver. 28 (IBM Corp., Armonk, NY, USA).

Baseline characteristics

The mean age of the participants was 44.6 years (95% CI, 44.3–44.8 years), and the mean follow-up duration was 7.85 years (95% CI, 7.78–7.93 years). There were 2,492 deaths (3.8% of all participants; 4.5% of male; 3.1% of female). Cancer mortality comprised 31.9% of all deaths, whereas cardiovascular mortality comprised 21.7%. All-cause mortality increased with lower BMI category, lower self-perceived weight, and underestimated weight. All-cause mortality was higher among participants with lower level of education or family income; those without spouses; smokers (current or former); those who did not consume alcohol; those who performed less physical activity; and those with depression, chronic illnesses, metabolic syndrome, or worse self-rated health (Table 1).

Self-perceived weight and all-cause mortality

The survival curve demonstrated that all-cause mortality varied during the follow-up period according to self-perceived weight. There was a tendency for the survival rate to decline when self-perceived weight decreased (Fig. 1). Table 2 shows the HRs of all-cause mortality according to self-perceived weight, weight perception, and the combinations of BMI categories and weight perception after adjusting for confounding factors. Compared to participants who self-perceived their weight to be just right, those who considered themselves very thin or thin had 1.68-fold and 1.43-fold greater all-cause mortality risks, respectively, even after adjusting for confounding variables, BMI category, and metabolic syndrome status. Compared with participants who accurately estimated their weight, those who underestimated their weight had a 27% lower all-cause mortality risk. After adjusting for confounding variables except for metabolic syndrome, all-cause mortality was higher among those who correctly recognized their underweight status, overestimated their underweight status, and underestimated their normal weight status than among those who accurately perceived their normal weight status (reference group). After further adjustment for metabolic syndrome, the risk of all-cause death was 2.14-times higher among those who accurately perceived themselves as underweight compared to the reference group; however, it was 47% lower among those who underestimated their obesity.

Self-perceived weight and cause-specific mortality

Associations between self-perceived weight-related indicators and mortality attributable to either cancer (Table 3) or cardiovascular disease (Table 4) were determined. Self-perceived weight was not associated with the risk of cancer mortality, whereas overestimation of weight was associated with a 2.89-fold higher risk of cancer death than appropriate estimation of weight. In particular, the risk of cancer mortality for participants who overestimated their underweight status was 3.94-times greater than that of the reference group (Table 3). Participants who perceived themselves as very thin had a 2.48-times higher risk of cardiovascular mortality than those who perceived their body shape as just right. In comparison to the reference group, the cardiovascular mortality risks were 2.32-times and 2.23-times higher among those who accurately estimated their underweight status and those who underestimated their normal weight, respectively (Table 4).

Self-perceived weight and all-cause mortality according to sex

Sex had a significant interaction with weight misperception among the self-perceived weight-related indicators of the total mortality risk. During the sex-specific analysis, among female, those who perceived themselves as very thin had a risk of all-cause mortality that was 1.87-times higher than that of those who perceived themselves as just right. Male who underestimated obesity had a 55% lower risk of all-cause mortality than those who accurately estimated their normal weight. In comparison to female who accurately estimated their normal weight status, the risk of all-cause mortality was 1.92-times higher among female who underestimated their normal weight. However, it was 28% lower among those who underestimated their obesity and 39% lower among those who correctly estimated their obesity (Table 5).

Using the linked dataset of the KNHANES and Causes of Death Statistics of Korean adults, this study suggested that even after adjusting for sociodemographic characteristics, health-related behaviors, underlying health status, BMI, and metabolic syndrome, self-perceived thinness was associated with a 43% to 68% increased risk of all-cause mortality during an average follow-up duration of 7.8 years. Compared to the normal weight group with accurate weight estimation, the risk of all-cause mortality was 2.14-times higher for the underweight group with accurate weight estimation. After controlling for the confounding factors, those who underestimated their weight had a 27% reduced risk of all-cause mortality compared to those who correctly estimated their weight. Additionally, compared with the group with normal weight who accurately perceived their weight, those with obesity who underestimated their weight had a 47% decreased risk of all-cause mortality. These results support the hypothesis that self-perceived weight is associated with mortality risk, regardless of whether it is considered independent of actual weight or along with actual weight.

These findings are significant because there have not been sufficient investigations of the relationship between subjective weight assessment and mortality risk. This study demonstrated that subjectively assessed weight remained an independent factor for predicting the risk of all-cause mortality despite the adjustment of factors that could have affected self-perceived weight.

During this study, the finding that a lower risk of all-cause mortality among those with obesity who underestimated their weight was partially consistent with the findings of a previous study.4 Using the KNHANES data, the odds ratio for worse self-rated health was lower for individuals who underestimated their weight and were overweight or obese.4 Additionally, a previous study demonstrated that individuals who underestimated their weight had a better quality of life.26 Furthermore, there is evidence that failing to recognize one’s own overweight status is associated with better health outcomes than correctly recognizing it.27 These findings might counter the idea that accurately identifying obesity is the first step in the process of helping individuals with obesity to manage their weight. In a meta-analysis, all-cause mortality was lowest with a BMI of 20 to 25 kg/m2, and it increased both immediately below this range and across the overweight and obesity ranges.15 Therefore, it is possible that those who are obese but underestimate their weight have a lower BMI in the category of obesity. Because there is a tendency for decreased risks of all-cause mortality and cardiovascular mortality, even for those who accurately perceived obesity, these findings may be related to inadequate adjustment of confounding factors.

The mechanisms underlying the increased all-cause mortality risk among participants who considered themselves to be thin, underestimated their weight, or accurately perceived their underweight status are unclear. This association remained consistent even after considering sociodemographic characteristics, underlying diseases, and health-related behaviors, which could influence how individuals perceives their own weight.1,28 The current findings may be explained by weak muscle strength because of the evidence that those who perceived themselves to be thin or underestimated their weight were more likely to have a lower grip strength29 and because of the evidence of the association between weak grip strength and increased mortality risk.30,31 The results of this study, which showed that self-perceived thinness was more strongly associated with cardiovascular mortality than cancer mortality, were also comparable to those of a previous study that showed that grip strength was more strongly related to cardiovascular mortality than to cancer mortality.32 An increased risk of cardiovascular mortality for participants who underestimated their normal weight or an increased risk of all-cause mortality for female who underestimated their normal weight may also be attributed to low muscle strength and its associated mechanisms.

The relationship between self-perception of thinness and a high risk of mortality may be related to the underlying reason for weight loss. This is because weight loss might be associated with being thin. Individuals who lose weight as a result of a condition that increases their mortality risk and who perceive themselves to be very thin are more likely to have the ability to accurately assess their weight status.

Body image disturbances may have contributed to an increased risk of cancer mortality among those who overestimated their weight (compared to those who accurately perceived their weight) and those who overestimated their underweight status (compared to those who accurately perceived their normal weight status). Overestimating body weight may result in inadequate eating behaviors and inappropriate weight management, which could increase the risk of mortality. Overestimating weight may be linked to dangerous weight loss approaches, such as vomiting and laxative use, as well as use of unhealthy coping strategies, such as stress-induced eating. Such behaviors can compromise health and cause eating disorders.11

No relevant studies have compared the findings of this study with those of others; therefore, future research is necessary. Additionally, because the types of cancer or cardiovascular diseases related to mortality may vary depending on self-perceived weight, additional research of the differences in the types of cancer or cardiovascular diseases as the cause of death and their associations with self-perceived thinness, accurately perceived underweight status, and overestimation of weight may be required.

It is well-established that underweight status increases the mortality risk. Individuals who are underweight and perceive themselves as thin can be categorized as a group at high risk for mortality if the findings of this study are practically implemented. Therefore, it will be useful to identify groups at high risk for mortality by considering the subjective perception of underweight status among those who are underweight. Additionally, the results of this study do not provide sufficient support to advise underestimating obesity, even though the mortality risk was lower among those who did. It would be preferable to investigate the characteristics of those who subjectively perceived their body shape as just right or slightly fat among those with a BMI ≥25 kg/m2 to determine whether the findings of this study are applicable.

This study had several limitations that should be considered. Although a 1-year time lag was introduced to exclude deaths at the beginning of follow-up, reverse causation in the relationship between self-perceived weight and risk of mortality may have been possible. Other limitations were that it did not analyze only non-smokers and did not exclude those with self-perceived very poor health, even after adjusting for smoking status and self-rated health. Because there may be more smokers or individuals with self-perceived very poor health among individuals who consider themselves to be very thin, additional research that specifically includes non-smokers or individuals with health conditions is necessary.

Additionally, this association could have been affected by confounding factors such as nutritional status, environmental factors, occupation, medication, sleep, and other mental health issues that were not considered. Another significant limitation was that the classification of weight perception differed based on the reference values for defining the BMI categories. Although the current study did not assess the relationship between self-perceived weight and mortality risk according to BMI-based weight categories, it is crucial to establish this relationship for this cohort if the follow-up period is extended.

In conclusion, this study demonstrates that self-perceived low body weight and accurately perceived underweight status among Korean adults are independent risk factors for increased risks of all-cause mortality and cardiovascular mortality. Instead of showing a greater risk of all-cause mortality for those with self-perceived obesity, the underestimation of obesity was associated with a lower risk of all-cause mortality. Long-term investigations that can establish the mechanism of this association and that consider factors that may affect causality are required.

The author declares no conflict of interest.

This study was supported by the 2022 JOMES Research Grant (Grant No. KSSO-J-2022004) of the Korean Society for the Study of Obesity. Data in this study were obtained from the Korea National Health and Nutrition Examination Survey, the Korea Disease Control and Prevention Agency, and the Cause of Death Statistics, Statistics Korea.

Fig. 1. Survival curve for all-cause mortality by self-perceived weight.

Comparison of characteristics between survivors and deceased (n= 42,453)

Variable Deceased (n) W%* Survivor (n) W%* Chi2 P
Number 2,492 3.8 39,961 96.2 -
Weighted N* 1,425,037 36,381,187 -
Cause of mortality -
Cancer 814 31.9 -
Cardiovascular disease 566 21.7 -
Others 1,112 46.4 -
BMI category (kg/m2) 11.7 < 0.001
< 18.5 194 5.9 1,706 94.1
18.5–< 22.9 1,066 4.0 15,937 96.0
23.0–< 24.9 577 3.8 9,458 96.2
≤ 25.0 655 3.2 12,860 96.8
Self-perceived weight 131 0.000
Very thin 352 12.7 1,606 87.3
Thin 497 5.4 4,845 94.6
Just right 1,059 4.0 16,351 96.0
Slightly fat 493 2.4 13,889 97.6
Very fat 91 1.5 3,270 98.5
Weight perception 41.9 0.000
Underestimation 1,227 4.8 15,906 95.2
Accurate estimation 1,128 3.3 20,392 96.7
Overestimation 137 2.2 3,663 97.8
Sex 48.5 < 0.001
Male 1,401 4.5 15,655 95.5
Female 1,091 3.1 24,306 96.9
Age (yr) 1,222 0.000
19–39 53 0.4 12,994 99.6
40–59 295 1.9 15,697 98.1
60–80 2,144 15.6 11,270 84.4
Education 666 0.000
< High school 1,908 10.2 13,610 89.8
High school 380 1.8 13,829 98.2
≥ College 175 1.0 11,973 99.0
Household income 347 0.000
1st quartile 1,264 11.6 7,068 88.4
2nd quartile 582 3.6 10,030 96.4
3rd quartile 319 1.8 11,103 98.2
4th quartile 255 1.7 11,298 98.3
Spouse 5.1 0.024
Yes 1,628 3.6 29,225 96.4
No 864 4.1 10,736 95.9
Smoker 75.9 0.000
Current 1,033 5.4 9,829 94.6
Former 379 4.1 5,143 95.9
Non 1,076 2.7 24,967 97.3
Alcohol drink (per month) 162 0.000
No 1,546 5.3 18,988 94.7
Yes 941 2.7 20,898 97.3
Physical activity 139 0.000
Regular 239 1.7 8,755 98.3
Irregular 2,231 4.5 30,653 95.5
Depression 32.7 < 0.001
No 1,949 3.8 30,988 96.2
Yes 435 5.5 4,885 94.5
Chronic diseases 264 0.000
No 105 0.8 7,923 99.2
Yes 2,387 4.7 32,038 95.3
Metabolic syndrome 263 0.000
No 1,146 2.5 27,024 97.5
Yes 898 6.2 9,814 93.8
Self-rated health 269 0.000
Very good/good 671 2.8 14,000 97.2
Fair 757 2.7 17,766 97.3
Poor/very poor 1,039 8.7 7,687 91.3

*Weighted percentage (W%) and weighted N were estimated by accounting for complex sampling design (strata, cluster, and sampling weight); P-value was based on Rao-Scott modified chi-square values.

Hazard ratios and 95% confidence intervals for the associations between self-perceived weight-related indicators and all-cause mortality

Weight indicator Death/person-year Adjusted HR (95% CI)

MV* MV+BMI MV+BMI+MetS
Self-perceived weight
Very thin 352/16,860 2.20 (1.68–2.89) 1.92 (1.36–2.69) 1.68 (1.15–2.46)
Thin 497/48,468 1.68 (1.28–2.23) 1.57 (1.16–2.12) 1.43 (1.04–1.99)
Just right 1,059/156,845 1.00 1.00 1.00
Slightly fat 493/131,050 0.89 (0.68–1.17) 1.05 (0.76–1.43) 1.16 (0.84–1.63)
Very fat 91/30,812 0.91 (0.57–1.46) 1.17 (0.70–1.93) 1.38 (0.80–2.36)
Weight perception
Underestimation 1,227/154,985 0.84 (0.70–1.02) 0.73 (0.58–0.90)
Accurate estimation 1,128/193,612 1.00 1.00
Overestimation 137/34,102 1.67 (1.07–2.61) 1.51 (0.90–2.48)
Combination of BMI category and weight perception
UW/accurate 101/5,906 2.18 (1.49–3.19) 2.14 (1.36–3.32)
UW/overestimation 93/10,826 1.93 (1.05–3.60) 1.57 (0.79–3.16)
NW/underestimation 214/9,364 1.70 (1.21–2.39) 1.45 (0.96–2.18)
NW/accurate 813/12,796 1.00 1.00
NW/overestimation 39/21,061 1.72 (0.92–3.19) 1.86 (0.98–3.53)
OW/underestimation 441/50,323 0.94 (0.70–1.25) 0.79 (0.57–1.07)
OW/accurate 131/38,049 0.94 (0.59–1.49) 0.94 (0.58–1.54)
OW/overestimation < 10/2,215§ 0.62 (0.15–2.53) 0.30 (0.07–1.25)
Obesity/underestimation 572/95,298 0.66 (0.51–0.86) 0.53 (0.39–0.73)
Obesity/accurate 83/27,861 0.75 (0.45–1.23) 0.68 (0.40–1.17)

All models accounted for complex sampling design (sampling weight, cluster, and strata). All HRs and 95% CIs were estimated by alternative models according to test for proportional hazard model assumptions.

*MV-adjusted model included age, sex, marital status, education, household income, smoking status, physical activity, alcohol drinking, self-rated health, depression, and chronic diseases status; Additionally adjusted for BMI category; Additionally adjusted for BMI category and MetS; §If there were < 10 deaths, the exact number was not given.

HR, hazard ratio; CI, confidence interval; MV, multivariable; BMI, body mass index; MetS, metabolic syndrome; UW, underweight; NW, normal weight; OW, overweight.

Hazard ratios and 95% confidence intervals for the associations between self-perceived weight-related indicators and cancer mortality

Weight indicator Death/person-year Adjusted HR (95% CI)

MV* MV+BMI MV+BMI+MetS
Self-perceived weight
Very thin 86/16,860 1.07 (0.79–1.44)* 1.14 (0.82–1.57)* 0.69 (0.36–1.31)
Thin 160/48,468 1.23 (0.94–1.62)* 1.28 (0.96–1.71)* 1.40 (0.82–2.44)
Just right 344/156,845 1.00 1.00 1.00
Slightly fat 188/131,050 1.26 (0.98–1.61)* 1.29 (0.99–1.67)* 1.26 (0.75–2.12)
Very fat 36/30,812 1.77 (1.14–2.75)* 1.90 (1.18–3.06)* 2.03 (0.87–4.81)
Weight perception
Underestimation 400/154,985 1.06 (0.76–1.48) 1.04 (0.72–1.51)
Accurate estimation 374/193,612 1.00 1.00
Overestimation 40/34,102 2.44 (1.32–4.53) 2.89 (1.49–5.58)
Combination of BMI category and weight perception
UW/accurate 23/5,906 0.63 (0.22–1.79) 0.79 (0.25–2.48)
UW/overestimation 23/10,826 3.22 (1.65–6.30) 3.94 (1.93–8.08)
NW/underestimation 56/9,364 0.95 (0.47–1.93) 0.79 (0.36–1.70)
NW/accurate 266/12,796 1.00 1.00
NW/overestimation 17/21,061 1.68 (0.57–5.00) 2.08 (0.64–6.69)
OW/underestimation 150/50,323 1.26 (0.79–1.99) 1.21 (0.73–2.01)
OW/accurate 50/38,049 0.68 (0.36–1.28) 0.73 (0.38–1.43)
OW/overestimation < 10/2,215§ - -
Obesity/underestimation 194/95,298 0.90 (0.58–1.38) 0.99 (0.61–1.62)
Obesity/accurate 35/27,861 1.92 (0.93–3.94) 1.88 (0.84–4.18)

All models accounted for complex sampling design (sampling weight, cluster, and strata). HRs and 95% CIs were estimated by *fitted Cox regression model or alternative models according to test for proportional hazard model assumptions.

*MV-adjusted model included age, sex, marital status, education, household income, smoking status, physical activity, alcohol drinking, self-rated health, depression, and chronic diseases status; Additionally adjusted for BMI category; Additionally adjusted for BMI category and MetS; §If there were < 10 deaths, the exact number was not given.

HR, hazard ratio; CI, confidence interval; MV, multivariable; BMI, body mass index; MetS, metabolic syndrome; UW, underweight; NW, normal weight; OW, overweight.

Hazard ratios and 95% confidence intervals for the associations between self-perceived weight-related indicators and cardiovascular mortality

Weight indicator Death/person-year Adjusted HR (95% CI)

MV* MV+BMI MV+BMI+MetS
Self-perceived weight
Very thin 81/16,860 1.90 (1.23–2.92) 2.03 (1.28–3.19) 2.48 (1.45–4.26)
Thin 106/48,468 1.15 (0.61–2.16) 1.22 (0.64–2.36) 1.54 (0.70–3.35)
Just right 243/156,845 1.00 1.00 1.00
Slightly fat 117/131,050 1.17 (0.70–1.93) 1.16 (0.64–2.12) 1.52 (0.81–2.86)
Very fat 19/30,812 0.89 (0.35–2.23) 0.91 (0.36–2.34) 1.15 (0.42–3.13)
Weight perception
Underestimation 296/154,985 1.11 (0.77–1.58) 1.15 (0.76–1.73)
Accurate estimation 244/193,612 1.00 1.00
Overestimation 26/34,102 0.86 (0.44–1.68) 0.84 (0.40–1.75)
Combination of BMI category and weight perception
UW/accurate 25/5,906 2.23 (1.25–4.01) 2.32 (1.21–4.48)
UW/overestimation 15/10,826 0.74 (0.29–1.92) 0.60 (0.17–1.93)
NW/underestimation 44/9,364 1.97 (1.08–3.60) 2.23 (1.13–4.44)
NW/accurate 174/12,796 1.00 1.00
NW/overestimation < 10/21,061§ 1.32 (0.52–3.35) 1.57 (0.60–4.06)
OW/underestimation 101/50,323 1.30 (0.76–2.23) 1.26 (0.68–2.34)
OW/accurate 29/38,049 1.48 (0.51–4.31) 1.63 (0.55–4.85)
OW/overestimation < 10/2,215§ 0.71 (0.13–3.94) 1.28 (0.24–6.69)
Obesity/underestimation 151/95,298 1.11 (0.70–1.73) 1.13 (0.66–1.90)
Obesity/accurate 16/27,861 0.93 (0.35–2.51) 1.01 (0.35–2.89)

All models accounted for complex sampling design (sampling weight, cluster, and strata). All HRs and 95% CIs were estimated by alternative models according to test for proportional hazard model assumptions.

*MV-adjusted model included age, sex, marital status, education, household income, smoking status, physical activity, alcohol drinking, self-rated health, depression, and chronic diseases status; Additionally adjusted for BMI category; Additionally adjusted for BMI category and metabolic syndrome; §If there were < 10 deaths, the exact number was not given.

HR, hazard ratio; CI, confidence interval; MV, multivariable; BMI, body mass index; MetS, metabolic syndrome; UW, underweight; NW, normal weight; OW, overweight.

Hazard ratios and 95% confidence intervals for the associations between self-perceived weight-related indicators and all-cause mortality by sex

Weight indicator Male Female P for interaction
Death/person-year 1,401/166,537 1,091/228,383 -
Self-perceived weight 0.115
Very thin 1.09 (0.66–1.84) 1.87 (1.35–2.60)*
Thin 1.42 (0.94–2.14) 1.19 (0.90–1.57)*
Just right 1.00 1.00
Slightly fat 1.39 (0.84–2.32) 0.80 (0.62–1.04)*
Very fat 1.35 (0.46–3.97) 0.74 (0.50–1.10)*
Weight perception 0.038
Underestimation 0.61 (0.45–1.22) 1.05 (0.86–1.28)*
Accurate estimation 1.00 1.00
Overestimation 1.29 (0.84–1.99)*
Combination of BMI category and weight perception 1.65 (0.92–2.94) 0.121
UW/accurate 1.58 (0.93–2.66) 1.54 (0.88–2.70)*
UW/overestimation 1.90 (0.97–3.71) 1.83 (0.96–3.48)*
NW/underestimation 0.93 (0.55–1.57) 1.92 (1.30–2.83)*
NW/accurate 1.00 1.00
NW/overestimation 1.77 (0.71–4.35) 0.93 (0.51–1.69)*
OW/underestimation 0.73 (0.49–1.09) 0.94 (0.71–1.24)*
OW/accurate 1.19 (0.66–2.14) 0.62 (0.42–0.90)*
OW/overestimation 0.02 (0.00–0.10) 0.53 (0.17–1.62)*
Obesity/underestimation 0.45 (0.29–0.68) 0.72 (0.56–0.93)*
Obesity/accurate 0.46 (0.16–1.36) 0.61 (0.42–0.89)*

All models were accounted for complex sampling design (sampling weight, cluster, and strata). HRs and 95% CIs were estimated by *fitted model of Cox regression model or alternative models according to test for proportional hazard model assumptions after adjusting for age, sex, marital status, education, household income, smoking status, physical activity, alcohol drinking, self-rated health, depression, chronic diseases status, BMI category (for the analysis of perceived body shape), and metabolic syndrome status.

BMI, body mass index; UW, underweight; NW, normal weight; OW, overweight.

  1. Herman KM, Hopman WM, Rosenberg MW. Self-rated health and life satisfaction among Canadian adults: associations of perceived weight status versus BMI. Qual Life Res 2013;22:2693-705.
    Pubmed CrossRef
  2. Idema CL, Roth SE, Upchurch DM. Weight perception and perceived attractiveness associated with self-rated health in young adults. Prev Med 2019;120:34-41.
    Pubmed CrossRef
  3. Park S, Lee S, Hwang J, Kwon JW. The impact of weight misperception on health-related quality of life in Korean adults (KN-HANES 2007-2014): a community-based cross-sectional study. BMJ Open 2017;7:e016098.
    Pubmed KoreaMed CrossRef
  4. Lee K. effects of weight misperception on the association between BMI and self-rated health in midlife and elderly Koreans. Arch Gerontol Geriatr 2022;100:104664.
    Pubmed CrossRef
  5. Sutin AR, Stephan Y, Terracciano A. Weight discrimination and risk of mortality. Psychol Sci 2015;26:1803-11.
    Pubmed KoreaMed CrossRef
  6. Sutin AR, Stephan Y, Robinson E, Daly M, Terracciano A. Perceived weight discrimination and risk of incident dementia. Int J Obes (Lond) 2019;43:1130-4.
    Pubmed KoreaMed CrossRef
  7. Jylhä M. What is self-rated health and why does it predict mortality? Towards a unified conceptual model. Soc Sci Med 2009;69:307-16.
    Pubmed CrossRef
  8. Wang C, Satariano WA. Self-rated current and future health independently predict subsequent mortality in an aging population. J Gerontol A Biol Sci Med Sci 2007;62:1428-34.
    Pubmed CrossRef
  9. Sutin AR, Terracciano A. Body weight misperception in adolescence and incident obesity in young adulthood. Psychol Sci 2015;26:507-11.
    Pubmed CrossRef
  10. Sonneville KR, Thurston IB, Milliren CE, Kamody RC, Gooding HC, Richmond TK. Helpful or harmful? Prospective association between weight misperception and weight gain among overweight and obese adolescents and young adults. Int J Obes (Lond) 2016;40:328-32.
    Pubmed CrossRef
  11. Haynes A, Kersbergen I, Sutin A, Daly M, Robinson E. A systematic review of the relationship between weight status perceptions and weight loss attempts, strategies, behaviours and outcomes. Obes Rev 2018;19:347-63.
    Pubmed KoreaMed CrossRef
  12. Chen C, Ye Y, Zhang Y, Pan XF, Pan A. Weight change across adulthood in relation to all cause and cause specific mortality: prospective cohort study. BMJ 2019;367:l5584.
    Pubmed KoreaMed CrossRef
  13. Berrington de Gonzalez A, Hartge P, Cerhan JR, Flint AJ, Hannan L, MacInnis RJ, et al. Body-mass index and mortality among 1.46 million white adults. N Engl J Med 2010;363:2211-9.
    Pubmed KoreaMed CrossRef
  14. Jee SH, Sull JW, Park J, Lee SY, Ohrr H, Guallar E, et al. Body-mass index and mortality in Korean men and women. N Engl J Med 2006;355:779-87.
    Pubmed CrossRef
  15. Di Angelantonio E, Bhupathiraju ShN, Wormser D, Gao P, Kaptoge S, et al; Global BMI Mortality Collaboration. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. Lancet 2016;388:776-86.
    Pubmed CrossRef
  16. Patel AV, Hildebrand JS, Gapstur SM. Body mass index and all-cause mortality in a large prospective cohort of white and black U.S. Adults. PLoS One 2014;9:e109153.
    Pubmed KoreaMed CrossRef
  17. Kweon S, Kim Y, Jang MJ, Kim Y, Kim K, Choi S, et al. Data resource profile: the Korea National Health and Nutrition Examination Survey (KNHANES). Int J Epidemiol 2014;43:69-77.
    Pubmed KoreaMed CrossRef
  18. Korea Disease Control and Prevention Agency. Guidebook for Korea National Health and Nutrition Examination Survey linked cause of death data [Internet]. Cheongju: Korea Disease Control and Prevention Agency [cited 2022 Aug 3]. Available from: https://knhanes.kdca.go.kr/knhanes/sub09/sub09_01.do.
  19. Yun S, Oh K. The Korea National Health and Nutrition Examination Survey data linked cause of death data. Epidemiol Health 2022;44:e2022021.
    Pubmed KoreaMed CrossRef
  20. Seo MH, Lee WY, Kim SS, Kang JH, Kang JH, Kim KK, et al. 2018 Korean Society for the Study of Obesity guideline for the management of obesity in Korea. J Obes Metab Syndr 2019;28:40-5.
    Pubmed KoreaMed CrossRef
  21. Korea Disease Control and Prevention Agency.
  22. Kim MK, Lee WY, Kang JH, Kang JH, Kim BT, Kim SM, et al. 2014 Clinical practice guidelines for overweight and obesity in Korea. Endocrinol Metab (Seoul) 2014;29:405-9.
    Pubmed KoreaMed CrossRef
  23. Alberti KG, Eckel RH, Grundy SM, Zimmet PZ, Cleeman JI, Donato KA, et al. Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. Circulation 2009;120:1640-5.
    Pubmed CrossRef
  24. Korea Centers for Disease Control and Prevention. The Sixth Korea National Health and Nutrition Examination Survey (KNHANES VI:2013-2015). Cheongju: Korea Centers for Disease Control and Prevention; 2015.
  25. Korea Centers for Disease Control and Prevention. Korea National Health and Nutrition Survey Guidelines for Analysis of Raw Data (SPSS). Cheongju: Korea Centers for Disease Control and Prevention; 2014.
  26. Hayward J, Millar L, Petersen S, Swinburn B, Lewis AJ. When ignorance is bliss: weight perception, body mass index and quality of life in adolescents. Int J Obes (Lond) 2014;38:1328-34.
    Pubmed KoreaMed CrossRef
  27. Robinson E, Haynes A, Sutin A, Daly M. Self-perception of overweight and obesity: a review of mental and physical health outcomes. Obes Sci Pract 2020;6:552-61.
    Pubmed KoreaMed CrossRef
  28. Grogan S. Body image and health: contemporary perspectives. J Health Psychol 2006;11:523-30.
    Pubmed CrossRef
  29. Lee K. Weight underestimation and weight nonregulation behavior may be related to weak grip strength. Nutr Res 2021;87:41-8.
    Pubmed CrossRef
  30. Kim S, Choi S, Yoo J, Lee J. Association of grip strength with all-cause mortality and cause-specific mortality: analysis of the Korean Longitudinal Study of Ageing (2006-2016). Korean J Fam Pract 2019;9:438-47.
    CrossRef
  31. Wu Y, Wang W, Liu T, Zhang D. Association of grip strength with risk of all-cause mortality, cardiovascular diseases, and cancer in community-dwelling populations: a meta-analysis of prospective cohort studies. J Am Med Dir Assoc 2017;18:551.e17-551.e35.
    Pubmed CrossRef
  32. Kim GR, Sun J, Han M, Park S, Nam CM. Impact of handgrip strength on cardiovascular, cancer and all-cause mortality in the Korean longitudinal study of ageing. BMJ Open 2019;9:e027019.
    Pubmed KoreaMed CrossRef