A healthy, balanced diet is important for keeping metabolic health and supporting immune system. Obesity is associated with a wide range of metabolic syndromes, including dyslipidemia, hyperglycemia and fatty liver. Hyperglycemia and lipid accumulation may provoke lipid oxidation and further lead to an overproduction of cytokines, hyperactivation of complement system and activation of coagulation system, which all serve as immunological triggers to severe infection of COVID-19 as well as other infectious diseases. With the soaring prevalence of cardiometabolic diseases attributed to obesity and metabolic syndrome, the significance of dietary factors in this context is becoming increasingly emphasized. Mirroring the obesity pandemic in adults, paediatric obesity is also rapidly growing worldwide. As a consequence, metabolic dysfunction-associated steatolic liver disease (MASLD) has become the most common liver disease affecting children1. A concern about paediatric liver diseases is that the disease is likely to persistent into adulthood, conferring a substantial cumulative risk of progressing into chronic liver disease, as well as cardiometabolic dysfunction2. Beyond examining individual dietary components, such as fruits or red meat individually, the impact of overall dietary patterns during childhood on indicators of overall health outcomes, such as blood glucose levels, blood pressure, liver fat and chronic inflammation, in adolescence and early adulthood remain inadequately understood. Moreover, the advent of advanced omics technologies, such as metabolomics, provides a promising approach to elucidate the intricate mechanisms/pathways linking dietary patterns to health outcomes. In the current proposed project, we will explore all the potential associations between dietary patterns and immune response, as well as potential metabolic-related mediators to explain the observed associations between diet and immune response through mediation analysis in the ALSPAC study.