A 2018 study published in NCBI aimed to compare the plausibility, safety, and efficacy of a low‐fat, high‐carbohydrate diet versus a ketogenic diet in PD patients. Primary outcomes were within‐ and between‐group changes in MDS‐UPDRS Parts 1 to 4 over 8 weeks. 47 patients were randomized, 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. The trial found that 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.