The Age‐Fit Hypothesis: Celebrity Age, Content Type, and Consumer Engagement on Social Media

Although prior work has examined celebrity influence in digital contexts, how celebrity age shapes follower responses to sponsored versus non‐sponsored content remains underexplored. Integrating role congruity theory with the ageing stability hypothesis, we propose an age‐fit hypothesis. We test this proposition across three studies using a multimethod design. Study 1 analyzes 22,619 posts from 286 celebrities. Study 2 applies sentiment analysis to 67,778 follower comments. Study 3 employs a 2 × 2 between‐subjects experiment ( N = 290) to replicate the interaction effect and test the underlying mechanism. Results consistently reveal that older celebrities elicit lower engagement and less positive emotional responses for sponsored posts relative to non‐sponsored posts, whereas younger celebrities elicit higher sponsored posts, with followers expressing more positive emotional responses toward their sponsored content. Study 3 further demonstrates that this interaction effect is sequentially mediated by perceived interest fit and social identification: reduced congruence between older celebrities and sponsored content diminishes followers’ interest alignment and identification, ultimately undermining engagement. By theorizing age‐based role congruity as a boundary condition in celebrity endorsement effectiveness, this research advances understanding of how stereotype‐driven identity processes shape consumer digital engagement.