Marjolein P. Schoonakker, Elske L. van den Burg, C.A. Sturm, H.J. Lamb, H. Pijl, M.E. Numans, M.A. Adriaanse, P.G. van Peet

Background

The Fasting In diabetes Treatment (FIT) trial showed that a fasting-mimicking diet (FMD) program, in addition to usual primary care, was effective in improving HbA1c levels and lowering glucose-lowering medication use in patients with type 2 diabetes (T2D). This mixed-methods sub-study aims to evaluate the feasibility of this approach.

Methods

Persons with T2D, using metformin only or no medication or for glycemic control, were randomly assigned to receive monthly 5-day FMD cycles plus usual care, or usual care alone for one year. FMD adherence was assessed by recording reasons for discontinuation, ketone measurements at 1, 4, 8 and 12 months and Diabetes Treatment Satisfaction Questionnaires at 3, 6, 9 and 12 months. Facilitators and barriers to FMD adherence were explored in focus groups.

Results

Of the 49 participants assigned to the FMD group, 15 participants (31%) discontinued the FMD due to diet-related issues and 4 participants (8%) due to issues unrelated to the FMD. Ketone levels were consistently higher in the FMD group than in the control group (p<0.0001). Treatment satisfaction did not differ between groups. Thematic analyses of the six focus groups (n=20) revealed three important themes regarding adherence: diet-related factors, health-related factors, and social interactions. Diet related facilitators included convenience, short duration of the FMD cycles, not feeling hungry, whereas barriers were the taste and quantity of the FMD and the frequency of the FMD cycles. Health related facilitators included internal motivation, believing in a beneficial effect on health of the FMD and experiencing improvements in health. Social support was an important facilitator whereas lack of social support and temptations in the environment were barriers.

Discussion/Conclusion

Periodic FMD appears feasible for persons with T2D in primary care based on adherence, ketone levels and treatment satisfaction. Feasibility might be enhanced by addressing identified facilitators and barriers regarding diet-related factors, health-related factors, and social interactions.