Feasibility of following a fasting-mimicking diet programme in persons with type 2 diabetes – a mixed-methods study

Background & Aims A fasting-mimicking programme in primary care demonstrated metabolic benefits for persons with type 2 diabetes (T2D). This study evaluated the feasibility of this approach. Methods Persons with T2D who used metformin or no medication for glycemic control, were randomly assigned to monthly 5-day fasting-mimicking diet (FMD) cycles plus usual care (n=51) or usual care alone (n=49) for one year. In this mixed method study, feasibility of following an FMD was evaluated by combining quantitative data, including reasons for discontinuation, serum ketone levels, and treatment satisfaction, and qualitative data from focus group discussions. Results In the FMD group, 61% of the participants completed the FMD programme, 31% discontinued the programme due to diet-related issues, and 8% discontinued the programme for other reasons. Ketone levels were consistently higher in the FMD group than in the control group (p<0.01). Treatment satisfaction did not differ between the groups. Focus groups (n=20) revealed facilitators of adherence, including convenience, short FMD cycles, not feeling hungry, internal motivation, believing in beneficial effects, experiencing health effects and social support. Barriers included taste, quantity, and frequency of the FMD, environmental temptations, and lack of social support. Conclusions The implementation of periodic FMD cycles appears feasible for T2D patients in primary care, supported by adherence rates, ketone levels, and treatment satisfaction. Adherence might be enhanced by addressing identified facilitators and barriers. Trial registration ClinicalTrials.gov; NCT03811587 . Registered 22 January 2019.