Background Irritable Bowel Syndrome (IBS) is a common functional gastrointestinal disorder characterized by abdominal pain, bloating, and altered bowel habits. Dietary patterns play a crucial role in symptom severity, yet their impact remains underexplored in young adults. Objective This study aimed to evaluate the association between different dietary patterns and IBS symptom severity in young adults. Methodology A cross-sectional study was conducted at the Medical Teaching Institute, Khalifa Gul Nawaz Teaching Hospital, Bannu, from May 1, 2023, to April 30, 2024. A total of 90 IBS patients were enrolled. Dietary patterns were categorized as Western diet, Mediterranean diet, Low-FODMAP diet, and Traditional Pakistani diet. IBS symptom severity was assessed using the IBS Symptom Severity Score (IBS-SSS). Statistical analyses included Chi-square tests, ANOVA, multiple logistic regression, and Pearson correlation analysis, using SPSS version 26.0. Results Conclusion Keywords The Western diet was associated with the highest IBS severity scores (280.6 ± 50.2, p = 0.003), while the Low-FODMAP diet had the lowest (150.3 ± 42.8). A significant positive correlation was found between processed food consumption and IBS severity (r = 0.52, p < 0.001), while fiber intake showed a negative correlation (r = -0.45, p = 0.001). Multiple logistic regression analysis confirmed that stress levels and physical activity influenced dietary impact on IBS severity. Dietary patterns significantly influence IBS symptom severity, with Western diets exacerbating symptoms, while Mediterranean and Low-FODMAP diets show a protective effect. These findings highlight the importance of dietary modifications in IBS management and support the need for personalized nutrition strategies for symptom relief.