The primary treatment for Parkinson's disease motor symptoms is levodopa, although it does not effectively address non-motor symptoms. A ketogenic diet may benefit patients by enhancing neuronal energy metabolism and addressing respiratory chain defects. While food can positively impact health and alleviate neuromuscular disease symptoms, there is a lack of studies on the ketogenic diet's effect in Parkinson's disease patients.

PubMed, EMBASE, Cochrane Central and Web of Science were used as search tools. The outcomes of interest selected were change in UPDRS I, II, III and IV, gastrointestinal side effects (nausea, vomiting, diarrhea, poor feeding),body weight loss (Kg) and adherence rate. Statistical analysis was performed using RevMan 5.1.7. 

402 articles were screened and 7 RCTs and (107 patients) were included. Ketogenic diet was associated with reduced UPDRS I (MD=-2.03; 95%CI [−3.84; −0.21]; p<0.01), UPDRS II (MD=−3.10; 95% CI [ −4.37; −1.82]; p=0.74;), UPDRS III (MD=−4.35; 95% CI [−6.74; −1.97]; p<0.01) and UPDRS IV (MD=−1.29; 95% CI [−2.16; −0.41]; p=0.22). Moreover, KD was associated with elevated gastrointestinal side effects (Events=9.69; 95% CI [2.64; 16.73]; p=0.19), body weight loss (MD=5.96; 95% CI [ 4.20; 7.72]; p=0.05), and adherence rate (Events=89.02; 95% CI [75.96; 100.00]; p=0.09).