Gut microbiota play a critical role in the development of intestinal cancer. Dietary changes cause dysbiosis of gut microbiota that mediates production of dietary factors triggering intestinal cancer. Genetic and dietary factors work in different combinatorial ways in initiation and progression of intestinal cancer, one of which is changes in gut microbiota. Recently, it has been found that high-fat-diet promote intestinal tumorigenesis in a genetically susceptible K-ras(G12Dint) mice without induction of obesity. High-fat-diet along with oncogene activation dampened paneth-cell mediated immunity and thus shift bacterial communities in such a way that promotes intestinal cancer.