 INNOVATION: Brain metabolism regulation and reduced neural inflammation via dietary approaches have only recently been explored in the treatmentmanagement of progressive cognitive disorders in humans. Preliminary results in Alzheimers and Parkinsons patients suggest that the use of ketones for brain fuel improves brain metabolism and cerebral perfusion as well as reduces accumulation of harmful brain proteins20 To date, the effects of a KD in cognitively impaired older HIV patients have not been explored. In addition, this study proposes the use of MRI testing to examine the longitudinal, physiologic changes in the brain of cognitively impaired, older HIV patients consuming a KD for 12 weeks. Moreover, this study will utilize the new FDA-approved Magnetom Prisma 3T MRI system to better visualize small-scale neural brain abnormalities. 