Ketone bodies, the products of fat metabolism, are a source of energy for the brain and are available even when glucose supplies are inadequate (such as with severe carbohydrate deprivation) or its metabolism is faulty (as it is in Alzheimer's disease). This phase I/II randomized clinical trial examined the feasibility of using a modified Atkins diet (MAD) to induce ketogenesis in persons with mild cognitive impairment (MCI) or early AD, and the effect of this diet on memory and other clinical outcomes. In the first 2.5 years of active recruitment, only 27 eligible and willing patients enrolled. After extensive assessment and education, they and their study partners were randomly assigned for 12 weeks to either the MAD or the National Institute on Aging (NIA) recommended diet for seniors. As of April 2018, 9 patients in the MAD arm and 5 in the NIA arm have completed the trial. In spite of extensive teaching, coaching, and monitoring, adherence to both diets was only fair. Among those in the MAD arm who generated at least trace amounts of urinary ketones, there was a large (effect size = 0.53) and statistically significant (p = 0.03) increase in Memory Composite Score between the baseline and week-6 assessment. MAD participants also reported increased energy between baseline and week-6 assessment. Despite challenges to implementing this trial, resulting in a small sample, our preliminary data suggest that the generation of even trace ketones might enhance episodic memory and patient-reported vitality in very early AD.