Effects of Ketogenic Diet on Quality of Life in Parkinson Disease: An Integrative Review

<i>Background/Aims</i>: Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the degeneration of dopaminergic neurons, leading to motor and non-motor symptoms that significantly impair quality of life (QoL). Oxidative stress (OS) and neuroinflammation play a key role in its progression. The ketogenic diet (KD) may have neuroprotective effects by reducing these factors through ketosis. The primary aim of this narrative review is to examine the impact of the ketogenic diet on the quality of life and symptomatology of patients with PD, evaluating its effects on motor and non-motor symptoms, as well as on certain metabolic parameters. Secondary aims included assessing the feasibility of and adherence to the diet, as well as its tolerability and safety. <i>Methods</i>: A search of PubMed, Scopus, Embase, CINAHL and Cochrane databases up to June 2025 was performed. Eligible studies included adults with PD following a KD regimen. Data were extracted regarding QoL outcomes, adverse events, and risk of bias included for synthesis. <i>Results</i>: A total of 152 patients were included across 6 studies. KD showed a small to moderate effect size on QoL improvements, particularly in non-motor domains such as fatigue and sleep quality. However, findings were inconsistent across studies. Risk of bias was rated moderate to high due to small sample sizes, heterogeneous methodologies, and lack of blinding. The most frequently reported adverse events were gastrointestinal disturbances (nausea, constipation), weight loss, and transient fatigue. <i>Conclusions</i>: Although preliminary evidence suggests a potential benefit of KD on QoL in PD patients, the small number of participants, short follow-up, and high heterogeneity significantly limit generalizability. Further large, controlled trials with rigorous methodology are warranted before relevant conclusion benefits can be drawn.