This chapter reviews how dietary fibers can be used to prevent Type 2 diabetes mellitus. Dietary fibers are a heterogenous group of food compounds. The physicochemical properties of dietary fibers determine their effects on gastrointestinal and metabolic health, including effect on gastro-intestinal transit, glycemic response, microbial composition and fermentative capacity. Most fiber rich foods contain insoluble, prebiotic and viscous fibers in varying ratios. The chapter begins by discussing underlying mechanisms of action of insoluble fibers. It then goes on to discuss the various dietary fiber intervention studies, specifically focusing on prebiotic fibers and soluble viscous fibers. The chapter concludes by highlighting the importance of consuming high levels dietary fiber and whole grains and their positive impact on metabolic health.