Obesity and diabetes are increasing worldwide, with serious medical and socio-economic consequences. Both are multifactorial diseases, influenced by genetic and environmental factors. Another common feature is the development of a chronic inflammatory process, which suggests that metabolic disorders alter the immune system. The human intestinal flora, in particular the microbial metabolites it produces, appear to play an important role in the development of obesity and diabetes, but the underlying mechanisms are still unclear. In our research projects, we want to use new methods (gnotobiotics, metagenomics and metabolomics) to investigate the complex interaction between gut flora, metabolism and immune function in order to understand how these factors contribute to the development of obesity and diabetes. In doing so, we aim to provide the foundation for new innovative strategies for the prevention and therapy of these important diseases.