The physical activity paradox in the development of metabolic syndrome: Based on the Korea National Health and nutrition examination survey

<i>Objectives</i>: Although physical activity is widely used to prevent metabolic syndrome, growing evidence suggests that occupational physical activity (OPA) may not confer the same health benefits as leisure-time physical activity (LTPA), a phenomenon known as the physical activity paradox. This study investigated the combined effects of OPA and LTPA on the risk of developing metabolic syndrome in a representative Korean adult population. <i>Methods</i>: We analyzed data from 18,691 adults aged ≥19 years who participated in the 2019-2021 Korea National Health and Nutrition Examination Survey. OPA and LTPA were categorized into low, moderate, and high levels based on standardized questionnaires. Metabolic syndrome was defined according to the modified National Cholesterol Education Program Adult Treatment Panel III criteria for the Korean population. Multivariable logistic regression was used to estimate odds ratios (ORs) for metabolic syndrome according to the combined OPA-LTPA categories, adjusting for demographic, socioeconomic, and behavioral variables. <i>Results</i>: Individuals with low OPA and moderate or high LTPA had significantly lower odds of developing metabolic syndrome than those with low OPA and low LTPA. A similar inverse association was observed among individuals with high OPA and moderate LTPA. However, no such benefit was observed among those with high OPA and LTPA, suggesting a potential overload effect of excessive total physical activity. <i>Conclusions</i>: These findings support the physical activity paradox and emphasize the need for domain-specific guidelines. Tailoring LTPA recommendations according to individuals' OPA levels may help optimize metabolic health benefits without contributing to cumulative physical overload.