How the ketogenic diet affects patients with Parkinson’s disease: A descriptive phenomenological study

Background: For individuals living with Parkinson’s disease (PD), the earliest and most disruptive changes are often not tremor or rigidity, but a gradual loss of mental clarity, physical confidence and social ease that reshapes everyday life. Aim: To explore how individuals with PD described changes in mental, physical and social quality of life (QoL) before and after participating in a 12-week low-carbohydrate, healthy-fat ketogenic dietary intervention. Setting: The study setting consisted of participants recruited through the Colorado Parkinson Foundation, a community-based organisation supporting individuals living with Parkinson’s disease and their caregivers. All participants resided in the United States during the study period. Methods: Sixteen adults diagnosed with PD, aged 36–81 years, participated in this descriptive phenomenological study. Participants were recruited with assistance from the Colorado Parkinson Foundation and resided in the United States. Semi-structured interviews were conducted via Zoom before and after the dietary intervention to capture participants’ lived experiences across time. Results: Pre-study interviews yielded three major themes describing participants’ experiences prior to dietary change, while post-study interviews yielded four major themes reflecting experiences following completion of the intervention. Participants described changes related to mental clarity, physical function, social engagement, metabolic health and relational support. Conclusion: Findings highlight how metabolic-based dietary intervention was experienced in everyday life by individuals living with PD. Participants described improvements in mental clarity, physical function and social engagement that corresponded to observed changes in metabolic health, suggesting a meaningful connection between metabolic adaptation and QoL. Contribution: Centring participant perspectives provides important patient-centred insight into how metabolic changes associated with a ketogenic diet (KD) intervention are experienced and integrated into QoL beyond clinical or biomarker outcomes.