BACKGROUND: The purpose of the current study was to investigate the association of obesity level, physical fitness level, hemoglobin A1c (HbA1c) level and metabolic syndrome (MetS) risk factors among Korean adults.METHODS: A total of 557 adults (272 males and 285 females) who underwent medical check-up at local hospital were recruited. In addition to regular health check-up, cardiopulmonary fitness, muscular endurance were measured and their association were analyzed.RESULTS: The prevalence of MetS was 31.7% for males and 23.7% for females. Females with the higher muscular endurance had lower waist circumference, triglyceride level, and HbA1c level than those with the lower muscular endurance. Males with the higher level of cardiopulmonary fitness had lower diastolic blood pressure, lower high-sensitivity C-reactive protein level and higher high density lipoprotein cholesterol level than males with the lower level of cardiopulmonary fitness. Females with the higher level of cardiopulmonary fitness had lower body weight, body mass index, systolic blood pressure, and fasting blood glucose level than females with the lower level of cardiopulmonary fitness. Participants with the higher level of adiposity and the lower level of physical fitness were 5.26 times (95% confidence interval [CI], 2.19 to 12.62), 5.71 times (95% CI, 2.23 to 14.60) more likely to have MetS, respectively, in male and female compared to participants who were neither obese nor have the lower level of fitness.CONCLUSION: This study suggests that maintaining a healthy body weight as well as a certain level of fitness is important for the prevention of MetS.