Temporal Trends of Association Between Physical Activity and Metabolic Syndrome in Korean Adults: A Nationwide Study in Korea (2018–2023)
Article information
Abstract
OBJECTIVES
The purpose of this study was to examine temporal trends in physical activity and metabolic syndrome (MetS) among Korean adults, and to evaluate secular trends in the association between physical activity and MetS from 2018 to 2023.
METHODS
This study utilized data from the Korea National Health and Nutrition Examination Survey (KNHANES) collected between 2018 and 2023. A total of 32,639 adults aged ≥ 19 years were included. Physical activity was dichotomized based on meeting the World Health Organization guidelines (≥ 150 minutes/week of moderate to vigorous physical activity). MetS was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria with Asian-specific waist circumference cutoffs, as the presence of ≥ 3 of 5 metabolic components based on measured component values. All analyses accounted for the complex sampling design of KNHANES by applying survey weights and primary sampling units and strata. Temporal trends were tested using orthogonal polynomial contrasts. Secular changes in the association between physical activity and MetS were evaluated using random-effects meta-regression.
RESULTS
Physical activity levels showed no significant temporal trends from 2018 to 2023. Among MetS components, waist circumference and HDL-C showed significant linear and quadratic trends, fasting plasma glucose demonstrated a significant quadratic pattern peaking in 2021, and both triglycerides and diastolic blood pressure showed significant negative linear trends, whereas systolic blood pressure showed no significant temporal trend. Pooled analyses revealed that meeting physical activity guidelines was associated with a 25% lower odds of MetS (pooled OR = 0.75, 95% CI = 0.70–0.80). Meta-regression indicated no significant secular change in this association across survey years.
CONCLUSIONS
Meeting physical activity guidelines was consistently associated with lower odds of MetS among Korean adults from 2018 to 2023, with no evidence of secular change in this association. Despite stable physical activity, several MetS components showed partially unfavorable temporal trends, underscoring the need for prevention strategies beyond physical activity alone.
Introduction
Physical activity is defined as any bodily movement generated by skeletal muscle contraction that results in energy expenditure [1]. Physical activity in daily life can be broadly categorized into occupational activities, active transportation, and leisure-time sports [2]. The World Health Organization (WHO) recommends that adults participate in at least 150 minutes of moderate-to-vigorous physical activity every week [3]. Regular physical activity is therefore considered essential for overall health, as adequate levels of physical activity have beneficial effects on weight management and the prevention of metabolic syndrome (MetS), cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) [4–6].
MetS refers to a condition that is a cluster of interrelated factors that directly increase the risk of coronary heart disease, CVD and T2DM [5]. According to the National Cholesterol Education Program’s Adult Treatment Panel III (NCEP-ATP III) criteria, MetS is diagnosed by the presence of three or more of the following five components, for which applies populationspecific cut-offs for abdominal obesity: 1) waist circumference (WC): men ≥ 90 cm, women ≥ 80 cm; 2) systolic blood pressure (SBP) ≥ 130 mmHg or diastolic blood pressure (DBP) ≥ 85 mmHg; 3) fasting plasma glucose ≥ 100 mg/dL; 4) triglycerides ≥ 150 mg/dL; 5) high-density lipoprotein cholesterol (HDL-C): men < 40 mg/dL, women < 50 mg/dL [6–8].
In South Korea, the burden of MetS has increased over time, potentially reflecting broader lifestyle changes such as reduced physical activity and shifts toward energy-dense dietary patterns. According to a previous study, the prevalence of MetS increased from 22.8% in 2007 to 28.6% in 2022 [9]. Notably, recent evidence suggests that MetS burden may have intensified during and after the COVID-19 pandemic, raising concerns about a further acceleration [10]. Physical activity is a modifiable behavior linked to adiposity, insulin sensitivity, blood pressure regulation, and lipid metabolism; insufficient physical activity is widely regarded as a key risk factor for MetS [11], whereas regular physical activity plays an important role in its prevention and management [12,13].
Although the inverse association between physical activity and MetS is well-established, whether and how the strength of this association has changed over time in the Korean population remains poorly understood [14]. Previous research has focused on associations rather than on investigating changes in the association between physical activity and MetS. Without understanding these temporal trends in the association itself, it is challenging to determine the extent to which changes such as declining or increasing physical activity contribute to MetS trends. Therefore, investigating this relationship over time is essential for identifying patterns that may inform targeted public health interventions [15]. In addition, analyzing these trends can help assess the effectiveness of public health policies aimed at promoting physical activity as a preventive measure against MetS and guide future health initiatives.
Therefore, the purposes of this study were to examine temporal trends in physical activity and MetS among Korean adults from 2018 to 2023, respectively, and to evaluate secular trends in the association between physical activity and MetS. In addition, we assessed the pooled association between physical activity and MetS across the Korea National Health and Nutrition Examination Survey (KNHANES) survey years 2018–2023.
Materials and Methods
Study Design and Participants
This study used the data from the KNHANES conducted between 2018 and 2023. KNHANES is an ongoing, nationally representative and cross-sectional survey designed to monitor the health and nutritional status of the Korean population. It has been conducted by the Korea Disease Control and Prevention Agency (KDCA) since 1998 [16]. The survey uses a multistage, stratified, clustered probability sampling design based on sex, age, and geographic region to ensure representativeness.
The survey consists of three main components: a health interview, health examination, and nutrition survey [16]. The data were collected through in-home interviews and standardized physical examinations carried out in mobile examination centers that were specially equipped for this purpose. The study protocol was approved by the Institutional Review Board of KDCA (2018-01-03-P-A; 2018-01-03-CA; 2018-01-03-2C-A; 2018-01-03-5C-A; 2018-01-03-4C-A; 2022-11-16-R-A). This secondary data analysis was approved with exempt status by the Institutional Review Board of Pusan National University (PNU IRB/2025_91_HR).
The study population consisted of adults aged 19 years and older. Participants with missing data on any of the five MetS components, physical activity, alcohol consumption, smoking status, education level, or other covariates used in the analysis were excluded. Following these exclusion steps, a total of 32,639 individuals were included in the primary analysis. For the analysis of physical activity trends, we further excluded participants with incomplete physical activity responses, resulting in a final sample of 22,025 participants.
Physical Activity
Physical activity was evaluated using the Korean adaptation of the International Physical Activity Questionnaire-Short Form (IPAQ-SF), implemented within the KNHANES survey. The IPAQ-SF is widely regarded as a valid and reliable instrument for assessing physical activity at the population level among adults across diverse environments [17]. This tool was utilized to capture weekly durations of walking, moderate-intensity and vigorous-intensity aerobic physical activity. According to established guidelines, total aerobic physical activity was derived by summing the weekly minutes of moderate-intensity physical activity and twice the minutes of vigorous-intensity physical activity. Walking was classified as low-intensity physical activity and was excluded from the total physical activity calculation. Based on the WHO guidelines, participants were categorized into two groups, with sufficient physical activity defined as performing at least 150 minutes of total physical activity per week [3].
Metabolic Syndrome
MetS was diagnosed according to the criteria defined by the NCEP-ATP III with Asian-specific waist circumference cutoffs [7,8], based on measured component values. Participants were classified as having MetS if they met at least three of the following conditions: 1) WC ≥ 90 cm in men or ≥ 80 cm in women; 2) SBP ≥ 130 mmHg or DBP ≥ 85 mmHg; 3) fasting plasma glucose levels ≥ 100 mg/dL; 4) triglyceride levels ≥ 150 mg/dL; 5) HDL-C levels < 40 mg/dL for men or < 50 mg/dL for women. WC was measured using a standard tape measure. SBP and DBP were measured with a mercury sphygmomanometer from 2018 to 2019, followed by the non-mercury Greenlight 300 device in 2020 and the Microlife WatchBP Office from 2021 to 2023. To address measurement differences due to device changes, blood pressure values from 2021 to 2023 were adjusted using the correction equation, while 2020 data were not corrected as differences were within acceptable limits compared with mercury sphygmomanometer measurements. Fasting plasma glucose, triglycerides, and HDL-C were analyzed through blood assays.
Covariates
The following covariates were considered as potential confounders in the analysis. Sex was categorized as male or female. Body mass index (BMI) was calculated as weight (kg) divided by the square of height (m2). According to the WHO Asia-Pacific classification [7], underweight was defined as BMI < 18.5 kg/m2, normal weight as 18.5 ≤ BMI < 23 kg/m2, overweight as 23 ≤ BMI < 25 kg/m2, and obesity as BMI ≥ 25 kg/m2. Smoking status was classified based on a lifetime consumption of at least 100 cigarettes, with individuals categorized as smokers or non-smokers. Alcohol consumption status was determined based on alcohol intake in the past year, with individuals classified as drinkers or non-drinkers. Sociodemographic covariates included education level categorized as less than elementary school, middle school graduate, high school graduate, and college graduate or higher. Additionally, household income quartiles were classified as lowest, lower-middle, upper-middle, and highest.
Statistical Analysis
All analyses conducted in Stata® (v. 12, StataCorp, College Station, TX, USA) took into account the complex sampling design of the survey; sample weights, primary sampling units, and clustering parameters were used to adjust for non-response, non-compliance, and to render nationally representative estimates.
Mean minutes of physical activity per week and mean values of the five diagnostic conditions of MetS across the cycles were determined. For each trend analysis, both linear and quadratic trends were tested using orthogonal polynomial coefficients. Multiple logistic regression was used to evaluate the association between meeting the physical activity guidelines and diagnostic conditions of MetS for each of the KNHANES cycles (2018–2023). In each model, covariates included age, sex, BMI, alcohol consumption, smoking status, education level, and household income quartiles.
Comprehensive Meta-analysis (CMA, Biostat Inc., Englewood, NJ, USA) software was used to evaluate the trend in the effect size (association) between meeting the physical activity guidelines and diagnostic conditions of MetS. Specifically, metaregression was used to examine the trend of the relationship between the observed odds ratios and the KNHANES cycles (years) utilizing a random-effects model (under the assumption of between-study heterogeneity). The degree of heterogeneity of the effect sizes was evaluated with the Cochran’s Q-statistic and the proportion of variation attributable to between-study heterogeneity was evaluated with I2 index. The significance level was set at 0.05.
Results
<Table 1> shows the weighted demographic characteristics across the KNHANES cycles from 2018 to 2023. Overall, the demographic characteristics, including age, sex, BMI, alcohol consumption, smoking status, education level, and household income remained relatively similar across the KNHANES cycles from 2018 to 2023. The weighted proportions of males, current drinkers, and smokers ranged from 49.24% to 50.11%, 72.75% to 76.87%, and 56.60% to 58.40%, respectively. For BMI categories, the participants’ underweight, normal weight, overweight, and obese proportions ranged from 3.72% to 4.48%, 33.86% to 38.87%, 21.56 to 22.86%, and 34.55% to 39.21%, respectively. The largest proportion of participants with a college degree or higher ranged from 51.67% to 56.44%. Lastly, the household income ranged from 13.47% to 15.78% in lowest, 21.73% to 25.12% in lower-middle, 27.05% to 30.41% in upper-middle, and 30.80% to 34.76% in highest.
<Table 2> indicates the trends in the weighted mean minutes of physical activity per week for the overall sample and subgroups across the KNHANES cycles from 2018 to 2023. For the overall sample, there were no linear or quadratic trends observed (Plinear = 0.17 and Pquadratic = 0.14) from 2018 to 2023. Subgroup analyses by sex, alcohol consumption, smoking status, education level, and household income quartile seem to have similar results. However, among BMI groups, the underweight group showed a significant quadratic trend (Pquadratic = 0.045) where the mean minutes of physical activity started at 336.73 in 2018, decreased to a low of 271.35 from 2019 to 2022, and then peaked at 368.85 in 2023.
<Table 3> presents the trends in the weighted mean values of the five diagnostic components of MetS, including WC, blood pressure, fasting plasma glucose, triglyceride levels, and HDL-C across the KNHANES cycles from 2018 to 2023. WC and HDL-C showed both linear and quadratic trends (Plinear < 0.001 and Pquadratic < 0.001). Fasting plasma glucose showed a quadratic trend (Pquadratic < 0.001), where the fasting plasma glucose peaked in 2021 (101.50 mg/dL) after increasing from 2018 (100.10 mg/dL), and then decreased to 99.08 mg/dL by 2023. Meanwhile, both triglycerides and DBP showed negative linear trends (Plinear < 0.001) while SBP showed no linear or quadratic trends (Plinear = 0.16 and Pquadratic = 0.08).
<Figure 1> illustrates the results for the association between meeting the physical activity guidelines and diagnostic conditions of MetS across the KNHANES cycles from 2018 to 2023. Pooled results across the cycles showed a statistically significant inverse association, with meeting the physical activity guidelines linked to 25% lower odds of MetS (Pooled OR = 0.75, 95% CI = 0.70–0.80, p < 0.001).
Odds of prevalence of MetS based on meeting physical activity guidelines.
As shown in <Figure 2>, meta-regression analyses revealed no statistically significant linear (β = -0.016, p = 0.44) or quadratic (β = -0.009, p = 0.51) trends in the association over cycles. Odds ratios consistently remained below 1 throughout all cycles, with a slight downward pattern. No evidence of heterogeneity was observed (Q(5) = 2.17, p = 0.82, I2 = 0%).
Trend in the association between meeting physical activity guidelines and prevalence of MetS.
Discussion
This nationally representative study of Korean adults from 2018 to 2023 examined (1) temporal trends in physical activity, (2) trends in MetS, and (3) secular trends in the association between meeting physical activity guidelines and MetS prevalence. These findings are particularly informative in the context of the COVID-19 pandemic, a period during which population-level health behaviors and metabolic risk were plausibly influenced.
In contrast to global reports indicating a significant decline in physical activity during the COVID-19 pandemic [18], our study found that the weighted mean minutes of physical activity per week remained relatively stable from 2018 to 2023, with no significant linear or quadratic trends in the overall sample. This pattern was consistent across most subgroups defined by sex, alcohol consumption, smoking status, educational level, and household income. Although the underweight BMI subgroup showed a statistically significant quadratic trend, it comprised a small proportion of the sample (approximately 4%), and the observed pattern should be interpreted cautiously.
Although physical activity remained relatively stable, several MetS components changed over time. WC showed both linear and quadratic trends across 2018–2023, increasing from 2018 to 2020 and remaining elevated thereafter with modest fluctuation. This mismatch (stable physical activity alongside increases in WC) may indicate that factors not captured by physical activity measures (e.g., sedentary behavior, dietary patterns, or broader lifestyle changes) could have contributed to the observed WC. These findings underscore the importance of prevention strategies that extend beyond physical activity promotion. Fasting plasma glucose demonstrated a significant quadratic trend, rising to a peak in 2021 and subsequently decreasing by 2023. This temporal pattern is consistent with a transient worsening of population glycemic status during the pandemic period, followed by partial improvement.
Lipid measures changed in a direction suggestive of improvement: triglycerides decreased over time. This is consistent with multicountry evidence showing recent declines in triglyceride levels, which may reflect gradual global improvement in lipid profiles at the population level [19]. HDL-C increased markedly—especially in 2022—with higher levels maintained in 2023. Blood pressure showed smaller shifts: diastolic blood pressure decreased modestly, whereas systolic blood pressure remained relatively stable. Taken together, these component-specific trends emphasize that cardiometabolic risk does not evolve uniformly and that different physiological domains may respond differently across the same societal period.
Meeting the physical activity guidelines was associated with lower odds of MetS across survey years, with a pooled estimate indicating approximately 25% lower odds among those meeting the guidelines. Meta-regression indicated no meaningful secular change in the magnitude of this association from 2018 to 2023, and between-year heterogeneity was not evident. These findings support the interpretation that adherence to recommended physical activity levels is associated with consistently lower MetS prevalence throughout the study period. From a prevention perspective, the stable inverse association aligns with physical activity as a durable intervention target. At the same time, the sustained elevation in waist circumference suggests that maintaining physical activity alone may be insufficient to counter population-level increases in central obesity. Strategies that combine physical activity promotion with weight-focused approaches are therefore likely to be required to reduce the total MetS burden.
However, interpretation of these findings should consider that physical activity was self-reported, repeated crosssectional surveys cannot establish causal effects or withinperson change, and the analyses did not directly incorporate several determinants that may shape MetS component trends (e.g., sedentary time, dietary intake, alcohol patterning, or psychosocial factors). Moreover, MetS components were classified based solely on measured values without accounting for medication use. As a result, some individuals receiving pharmacologic treatment may have had component values controlled below the diagnostic cutoffs, which could lead to an underestimation of MetS and warrant cautious interpretation of the findings. Future studies that integrate objective activity and sedentary measures, richer behavioral/clinical covariates, and longitudinal follow-up would help clarify mechanisms underlying the observed component-specific trends—particularly the rise and persistence of abdominal obesity—and strengthen causal inference regarding the physical activity–MetS relationship.
The present study has several notable strengths. It utilized a large, nationally representative dataset with strong external validity, evaluated temporal trends using meta-regression, and conducted subgroup analyses that supported the consistency of the main association across key population strata.
Conclusions
This study examined temporal trends in physical activity and MetS and evaluated secular changes in the association between physical activity and MetS among Korean adults from 2018 to 2023. Overall, physical activity levels remained relatively stable across the study period, whereas several MetS components, including WC and fasting plasma glucose, showed partially unfavorable temporal changes. Across survey years, meeting physical activity guidelines was consistently associated with lower odds of MetS, with no evidence of secular change in this association. These findings underscore the continued public health importance of promoting adherence to physical activity guidelines while also highlighting the need for complementary strategies targeting central adiposity and other metabolic risk factors in Korean adults.
Notes
There are no conflicts of interest for any of the listed authors.