The coronavirus disease 2019 pandemic induced global lifestyle changes that have impacted public health, particularly concerning obesity. This study investigated the changes in obesity prevalence and associated factors among Korean adults using data from the Eighth Korea National Health and Nutrition Examination Survey (KNHANES VIII, 2019~2021). The participants were divided into pre-pandemic (2019) and pandemic (2020~2021) groups. The results suggested that the prevalence of obesity and perceived weight gain increased significantly during the pandemic. Regarding dietary habits, while mixed grain consumption increased, fruit intake decreased, particularly among women.In addition, men showed a specific increase in saturated fat intake. Although moderateintensity physical activity increased, high-frequency walking declined during the pandemic.The pandemic period was associated with a significantly higher risk of obesity (odds ratio [OR]: 1.17, 95% confidence interval [CI]: 1.03~1.32) compared to 2019. Factors significantly associated with obesity included men, age 30 years or older, rural residence, lower education levels, and lower Korean Healthy Eating Index (KHEI) scores. Therefore, the pandemic-related rise in obesity may be closely linked to diet quality and educational level rather than to changes in physical activity alone. Consequently, post-pandemic public health strategies should prioritize nutrition education and targeted interventions for vulnerable populations, particularly those with lower educational attainment.