BACKGROUND/OBJECTIVES: The coronavirus disease 2019 (COVID-19) pandemic has affected the entire world population in many ways. This study aimed to analyze the patterns of changes in eating, food purchasing and preparation, physical activity, and subjective health after COVID-19 outbreak by various sociodemographic factors and to understand the factors associated with changes in subjective health. SUBJECTS/METHODS: A cross-sectional survey using a representative sample from Seoul was used for the analysis. The data collection was conducted from September to October 2020. A total of 3,833 citizens aged more than 18 years old participated in the Seoul Food Survey. Descriptive statistics and generalized ordinal logistic regression models were used to understand the changes in health behaviors, health indicators, and subjective general health by various socioeconomic status. RESULTS: It was shown that the changes in household income, food expenditure, food consumption and physical activities differed significantly by age, education, occupation, income, weight, and food security status. Low-income and food-insecure households were affected more severely by the pandemic. Older age, household food insecurity, income reduction, increased home cooking and frequency of having instant foods, decreased physical activity and weight gain were significant factors explaining worse perceived health during the COVID-19 pandemic. CONCLUSIONS The results suggest that focusing on older populations and low-income families with food insecurity should be prioritized during infectious disease outbreaks. In addition, the role of physical activities and instant food consumption in explaining perceived health should be investigated further in this prolonged battle with the pandemic situation.