Objectives: The aim of this study was to examine the relationship between periodontitis, obesity, and health behavior according to sex and age in Korean adults. Methods: Data on 11,032 adults aged 19-79 years were obtained from the 7th Korea National Health and Nutrition Examination Survey (KNHNES). We used multivariate logistic regression analysis to test for associations. Results: The final model that was adjusted for demographic characteristics and health status, showed a higher risk of periodontitis with increasing body mass index (BMI), smoking, failure to use oral care products, and no dental check up. In the sub-group analysis, only smoking was significant in the 19 to 39-year-old age groups. In the 40 to 64-year-old age group, a BMI of 30 or higher, and smoking, use of oral care products, and dental check-up were significantly associated with periodontitis. In the female group, BMI, smoking, use of oral care products, and dental check-up were significantly related to periodontitis. However, in males, only smoking was significant. Conclusions: Obesity management can be helpful for periodontal health as periodontitis prevalence in adults increased as BMI increased. For periodontal health, an oral health program should include smoking cessation and the use of oral care products and dental check up as part of obesity management.