Abstract
Abnormal body weight has become an increasingly prominent public health concern in China. In response, national health authorities launched a three-year Weight Management Year campaign, disseminating extensive online risk communication to promote public awareness and healthier lifestyles. Despite these efforts, reader engagement (RE) varies substantially, raising questions about how health risk can be communicated more effective. Previous studies have explored various antecedents of RE, but often in isolation, making it difficult to capture the complex interplay of factors in real-world settings. Grounded in the heuristic-systematic model, this study applies crisp-set qualitative comparative analysis to examine conjunctural causation among three systematic and two heuristic cues in shaping RE across 61 WeChat articles issued by health authorities and hospitals. The analysis identifies four pathways leading to strong engagement and six pathways resulting in weak engagement. Strong RE appears to emerges through systematic-dominant, heuristic-compensatory, and dual-cue reinforcing configurations, whereas weak RE reflect mismatches between message features and audience expectations or limited heuristic support. Overall, the findings reveal causal asymmetry and multiple conjunctural causation in RE, highlighting the complexity of online health communication and the need for context-sensitive communication strategies.