The booming nature of influencer marketing has radically changed the way consumer trust is developed in fitness markets, where credibility indicators have a direct influence on attitudes, behavioural intentions, and health decision-making. The presented meta-analytical review also summarizes and critically reviews the available research on credibility in the role of influencers and consumer trust, focusing specifically on the contexts related to fitness on social media platforms. The review relies solely on a few peer-reviewed sources to synthesize the findings of social media marketing, consumer behavior, and influencer effectiveness studies and detect the common trends, theoretical underpinnings, and gaps in research. The previous meta-analytical and extensive empirical investigations demonstrate that the credibility of influencers, which is expressed through their expertise, trustworthiness, authenticity, and self-brand congruity, significantly impacts trust, engagement, and the intent to purchase or participate. Nonetheless, there is also evidence of significant heterogeneity, which is platform affordance led and is influenced by the types of influencers (macro and micro), the audience participation, and the type of sensibilities of the domain, which is specific to fitness and health consumption. The current review contributes to the literature by organizing the relationship between the dimensions of influencer credibility and the outcomes of trust in the context of the fitness market, which depicts a theoretical gap and a lack of methodological power of available investigations. Combining the knowledge on marketing, psychology, and digital health research, the paper suggests an integrative approach that elucidates the way and under what circumstances influencer credibility converts into consumer trust. The results of the study provide a stringent basis for future theory advancement and evidence-based management techniques in ethically sensitive fitness and wellness markets.