Endorsement model’s body size: advertising effectiveness to diet food purchase intention through digital celebrity credibility

This study aims to explore the effects of body size and appearance – homophily on parasocial interaction (PSI), advertisement recognition, and purchase intention of diet food products promoted by digital celebrities on the social media platform, TikTok. The main focus is to understand how body size and appearance - homophily can influence advertisement effectiveness and purchase decisions, considering the moderating role of digital celebrity credibility. A total of 357 data were collected through an online survey, verified, and analyzed using PLS-SEM. The results showed that advertisement model body size and appearance – homophily had a positive effect on PSI and advertisement recognition. Moreover, PSI was significant in increasing purchase intention of diet food products but advertisement recognition had no direct effect. It was also observed that digital celebrity credibility acted as a moderator to strengthen the relationship between model body size and PSI as well as ad recognition to increase purchase intention. This study provided important insights for marketers on how to select the right digital celebrities based on body size and appearance – homophily to enhance advertising effectiveness on social media. The results showed that digital celebrity credibility could strengthen or weaken the influence of body size on advertising outcomes, especially in sensitive products such as diet food. The original contribution provided is by examining the influence of body size, appearance - homophily, and digital celebrity credibility in the context of social media, specifically TikTok which is an increasingly dominant platform in digital advertising. The results extend the literature on digital celebrities and parasocial interactions, and subsequent application in the marketing of health and weight loss products.