With the development of information technology and the popularization of the O2O business model, food delivery services have become a primary dietary choice for university students. This study, based on the social-ecological model, environmental psychology, and behavioral decision theory, aims to explore the mechanisms by which food delivery culture and campus dining environments influence obesity risk among university students, providing a basis for campus dietary management and public health policies. The study involved eight universities in Changsha, collecting 518 questionnaires on dietary behaviors, self-reported BMI, and weight change data. It also integrated data from Gaode Maps and food delivery platforms to assess the characteristics of dining environments. Multiple regression and logistic regression models were used to analyze the relationships between dining environments, food delivery frequency, and health outcomes. The results showed that food delivery frequency was significantly associated with economic status (regression coefficient = 0.418,