Despite unprecedented digital measurement capabilities, the causal effect of influencer marketing on business performance has eluded systematic quantification. This thesis addresses that gap through rigorous empirical investigation of the high-end restaurant sector, motivated by a central managerial question: is it more effective to invest in external influencer collaborations or in cultivating owned brand identity? The thesis adopts a dual approach. First, a cross-sector literature review integrates academic research with Harvard Business School case studies to map knowledge at the intersection of strategic marketing, brand equity, and influencer dynamics, synthesizing evidence from fashion, entertainment, sports, and consumer goods. Second, original empirical analysis examines 348 Michelin-starred Italian restaurants over seven years (June 2018–June 2025), leveraging Google Trends data and staggered YouTube video coverage from three major Italian food content creators to implement a difference-in-differences identification strategy.