Sedentary behaviour (SB) is an independent health risk that remains widely misunderstood, with many individuals believing that regular physical activity fully offsets the risks of prolonged sitting. While public health campaigns often emphasize the importance and severity of sedentary behaviour to encourage behaviour change, persuasive health communication may paradoxically become less effective when messages threaten existing beliefs or self-perceptions.

To investigate this possibility, this study experimentally examined whether emphasizing the importance of sedentary behaviour as a health issue reduces the effectiveness of persuasive health messages. This study proposes that stressing the importance of a health message may motivate individuals to defend their existing beliefs rather than change their attitudes. Using a 2 × 2 experimental design, the study examines whether importance framing reduces attitude change in response to persuasive health messages about sedentary behaviour and whether this effect is mediated by belief consistency.