While the study investigators and others have demonstrated links between IR and CBF as well as cognition from an observational perspective, no studies have investigated CBF and cognition after an intervention involving exercise and a carbohydrate restricted diet (CRD) designed to improve or normalize IR and glucose homeostasis. The study investigators propose to determine the effect of improving or normalizing glucose homeostasis on CBF and cognition, through diet and exercise, in individuals with IR and at risk for the development of AD.