Nutritional properties of starch in foods are to a large extent related to its availability for digestion and absorption in the gastrointestinal tract. Resistant starches, in particular which produce large reductions in postprandial metabolic responses may appear to have long-term benefits related to diabetecs and hyperlipidemia. It is therefore of importance to understand the gastrointestinal fate of resistant starch to predict any kind of physiological effects. This paper will focus on in vitro and in vivo determinations of resistant starch and discuss the protective effect of resistant starch in the development of insulin resistance in rats.