结直肠癌是全球常见恶性肿瘤之一，在西方国家尤其常见。饮食是结直肠癌的重要影响因素之一。近年来，随着 我国社会经济的不断发展，结直肠癌发病率出现了逐年上升以及年轻化的现象，推测可能与西方高脂饮食流行、肥胖、运动缺 乏等因素相关。高脂饮食与结直肠癌的发生发展紧密相关。高脂饮食可引起肠道菌群结构改变，具体表现为肠道微生态多样 性的下降，以及拟杆菌属菌丰度降低和厚壁菌门细菌的富集，同时还可对肠道菌群代谢产生重要影响，产生大量次级胆汁酸、 脂肪酸和硫化物衍生物等。其中，过量的次级胆汁酸具有促进结直肠肿瘤发生发展的作用。次级胆汁酸可引起肠道上皮细胞 DNA损伤，加剧炎症反应，同时还可促进肠道类干性样细胞‐Lgr5（+）细胞的增殖，从而促进结直肠癌的发生发展。本文将围绕 高脂饮食对结直肠癌发生发展的影响、膳食脂肪对肠道菌群的影响、膳食脂肪对肠道菌群代谢的影响，以及结直肠癌的饮食预 防进行介绍和讨论。

Colorectal cancer (CRC) is one of the most common cancers worldwide, especially in western countries. Diet is one of the major factors that contribute to the development of CRC. In recent years, with the development and improvement of social economy in our country, the CRC incidence has been rising with increased trend of young⁃onset cases, which is probably associated with high fat diet, obesity and lack of physical exercises. Studies have shown that high fat diet is closely associated with CRC. High fat diet could alter gut microbiota composition with decreased bacterial diversity along with depletion of Bacteroides and enrichment of Firmicutes. Furthermore, high fat diet could also have an impact on gut metabolites with increased secondary bile acids, fatty acids and sulfide derivants. Studies have demonstrated that excess secondary bile acids could lead to DNA damage and gut inflammation in colon epithelial cells, and also promote proliferation of colon stem⁃like cell⁃Lgr5(+) cells and thus contributing to colorectal tumorigenesis. In this review paper, we will discuss the contribution of high fat diet on colorectal tumorigenesis, the impact of dietary fat on gut microbiota and metabolites, and also dietary strategies for the prevention of CRC.