Low‐fat versus ketogenic diet in Parkinson's disease: A pilot randomized controlled trial

Background: Preliminary evidence suggests that diet manipulation may influence motor and nonmotor symptoms in PD, but conflict exists regarding the ideal fat to carbohydrate ratio. Objectives: We designed a pilot randomized, controlled trial to compare the plausibility, safety, and efficacy of a low‐fat, high‐carbohydrate diet versus a ketogenic diet in a hospital clinic of PD patients. Methods: We developed a protocol to support PD patients in a diet study and randomly assigned patients to a low‐fat or ketogenic diet. Primary outcomes were within‐ and between‐group changes in MDS‐UPDRS Parts 1 to 4 over 8 weeks. Results: We randomized 47 patients, of which 44 commenced the diets and 38 completed the study (86% completion rate for patients commencing the diets). The ketogenic diet group maintained physiological ketosis. Both groups significantly decreased their MDS‐UPDRS scores, but the ketogenic group decreased more in Part 1 (−4.58 ± 2.17 points, representing a 41% improvement in baseline Part 1 scores) compared to the low‐fat group (−0.99 ± 3.63 points, representing an 11% improvement) (P < 0.001), with the largest between‐group decreases observed for urinary problems, pain and other sensations, fatigue, daytime sleepiness, and cognitive impairment. There were no between‐group differences in the magnitude of decrease for Parts 2 to 4. The most common adverse effects were excessive hunger in the low‐fat group and intermittent exacerbation of the PD tremor and/or rigidity in the ketogenic group. Conclusions: It is plausible and safe for PD patients to maintain a low‐fat or ketogenic diet for 8 weeks. Both diet groups significantly improved in motor and nonmotor symptoms; however, the ketogenic group showed greater improvements in nonmotor symptoms. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.