Online-to-offline (O2O) food delivery platforms have greatly expanded urban residents' access to a wide range of food options by allowing convenient ordering from distant food outlets. However, concerns persist regarding the nutritional quality of delivered food, particularly as the impact of O2O food delivery platforms on users' healthy food remains unclear. This study leverages large-scale empirical data from a leading O2O delivery platform to comprehensively analyze online food choice behaviors and how they are influenced by the online exposure to fast food restaurants, i.e., online food environment. Our analyses reveal significant variations in food preferences across demographic groups and city sizes, where male, low-income, and younger users are more likely to order fast food via O2O platforms. Besides, we also perform a comparative analysis on the food exposure differences in offline and online environments, confirming that the extended service ranges of O2O platforms can create larger "cyber food swamps". Furthermore, regression analysis highlights that a higher ratio of fast food orders is associated with "cyber food swamps", areas characterized by a higher proportion of accessible fast food restaurants. A 10% increase in this proportion raises the probability of ordering fast food by 22.0%. Moreover, a quasi-natural experiment substantiates the long-term causal effect of online food environment changes on healthy food choices. These findings underscore the need for O2O food delivery platforms to address the health implications of online food choice exposure, offering critical insights for stakeholders aiming to improve dietary health among urban populations.

翻译：线上到线下（O2O）外卖平台通过允许用户便捷地从较远餐饮店订购，极大地扩展了城市居民获取多样化食品的渠道。然而，关于配送食品营养质量的担忧持续存在，尤其是O2O外卖平台对用户健康食品选择的影响尚不明确。本研究利用一家领先O2O外卖平台的大规模实证数据，全面分析了在线食品选择行为及其如何受到在线快餐店暴露（即在线食品环境）的影响。我们的分析揭示了不同人口群体和城市规模间食品偏好的显著差异，其中男性、低收入和年轻用户更倾向于通过O2O平台订购快餐。此外，我们还对线下与在线环境中的食品暴露差异进行了比较分析，证实O2O平台扩大的服务范围可能形成更大的“网络食品沼泽”。进一步的回归分析表明，较高的快餐订单比例与“网络食品沼泽”相关，这些区域以较高比例的可访问快餐店为特征。该比例每增加10%，订购快餐的概率将上升22.0%。此外，一项准自然实验证实了在线食品环境变化对健康食品选择的长期因果效应。这些发现强调了O2O外卖平台需要关注在线食品选择暴露的健康影响，为旨在改善城市人口膳食健康的利益相关者提供了重要见解。