The human gut microbiome is a complex and dynamic ecosystem that plays a crucial role in maintaining host health. Previous research has demonstrated that diet significantly impacts microbiome composition and diversity. This study aims to investigate the effects of various dietary components on gut microbiome diversity across different populations. Utilizing a cohort derived from three distinct geographical regions—Asia, Europe, and South America—we employed high-throughput sequencing to analyze microbiome samples. The study focused on dietary intake data, which were collected and categorized into macronutrient groups. Our findings reveal significant correlations between high fiber diets and increased microbial diversity, whereas high-fat diets were associated with a reduction in diversity. Interestingly, geographical and cultural food practices also exhibited distinct microbial compositions, underscoring the importance of environment on gut microbiota. The study concludes that dietary interventions could be a strategic approach to manipulate the gut microbiome, potentially improving health outcomes. These insights contribute to the growing understanding of diet-microbiome interactions and highlight the need for personalized nutritional strategies.