Online-to-offline (O2O) food delivery platforms have substantially enriched the food choices of urban residents by allowing them to conveniently access farther food outlets. However, concerns about the healthiness of delivered food persist, especially because the impact of O2O food delivery platforms on users' healthy food choices 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 discrepancy in food preferences across demographic groups and city sizes, where male, low-income, and younger users and those located in larger cities more likely to order fast food via O2O platforms. Besides, we also perform a comparative analysis on the food exposure differences in online and offline 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 share of accessible fast food restaurants. A 10% increase in this share 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. Our findings underscore the need for O2O food delivery platforms to address the health implications of online food choice exposure, thereby informing efforts by various stakeholders to improve residents' dietary health.

翻译：线上到线下（O2O）食品配送平台通过使用户能够便捷地获取更远距离的餐饮商家，极大地丰富了城市居民的食品选择。然而，关于配送食品健康性的担忧持续存在，尤其是因为O2O食品配送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配送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接触快餐店（即在线食品环境）的影响。我们的分析揭示了不同人口统计群体和城市规模之间食品偏好的显著差异，其中男性、低收入、年轻用户以及位于较大城市的用户更有可能通过O2O平台订购快餐。此外，我们还对线上和线下环境中的食品接触差异进行了比较分析，证实O2O平台扩展的服务范围可以形成更大的“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，这些区域的特征是可访问的快餐店占比较高。该比例每增加10%，订购快餐的概率将提高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。我们的研究结果强调了O2O食品配送平台需要关注在线食品选择接触对健康的影响，从而为各利益相关方改善居民膳食健康的努力提供参考。