Pilot study of a ketogenic diet in bipolar disorder: a process evaluation

Abstract

Background: Bipolar disorder is a serious mental illness, which requires new strategies for prevention and management. Recent evidence suggests that a ketogenic diet may be an effective intervention. This research aimed to explore the feasibility and acceptability of a ketogenic diet intervention for bipolar disorder, fidelity to its behavioural components and the experiences of the participants and research clinicians involved. Methods: A mixed-methods process evaluation was conducted. Semi-structured telephone interviews were carried out with 15 participants 1-2 months after completing a 6-8 week modified ketogenic diet intervention, and 4 research clinicians from the study team following the completion of data collection. Data were thematically analysed. Fidelity checklists completed by research dietitians were analysed using descriptive count and percentage statistics. Findings are reported post-hoc, following the analysis and publication of the main pilot study findings. Results: Qualitative data indicated that participants had various motives for taking part in the study, including weight loss. It was important to support people's motives while facilitating clear and realistic expectations. Despite the challenges of initiating and maintaining a ketogenic diet, including for some its disruptive effects on daily living, many participants perceived physical and psychological benefits (e.g. significant weight loss, mood stability and an enhanced ability to focus). A range of behavioural (e.g. goal setting), social (e.g. family and dietitians) and technological (e.g. apps for monitoring) support mechanisms were generally considered key facilitating factors. Meanwhile, dietary preferences, concerns about the diet and its impact, the testing burden and capacity of the delivery team were perceived as barriers for some. The importance of wider contextual influences (e.g. the cost of living and sociocultural expectations) were highlighted. Overall, descriptive analyses indicated moderate-to-good fidelity to the behaviour change components of the study. Conclusion: We provide novel insight into the experiences of people living with bipolar disorder initiating and following a ketogenic diet, as well as those of research clinicians who support the intervention. Future trials may benefit from increased clinical research capacity, better-defined entry and exit routes, additional interpersonal support, and greater understanding of how social and societal factors impact participation.