Fasting in diabetes treatment (FIT) trial: study protocol for a randomised, controlled, assessor-blinded intervention trial on the effects of intermittent use of a fasting-mimicking diet in patients with type 2 diabetes

Abstract Background Caloric restriction is an effective way to treat Type 2 diabetes (T2D). However, chronic and severe restriction of food intake is difficult to sustain and is known to promote slower metabolism. Intermittent and frequent fasting can exert similar metabolic effects, but may be even more challenging for most patients. A fasting-mimicking diet (FMD) is low in calories, sugars and proteins, but includes relatively high levels of plant based complex carbohydrates and healthy fats. The metabolic effects of such a diet mimic the benefits of water-only fasting. The effects of a FMD applied periodically in T2D patients are still unknown. The Fasting In diabetes Treatment (FIT) trial was designed to determine the effect of intermittent use (5 consecutive days a month during a year) of a FMD in T2D patients on metabolic parameters and T2D medication use compared to usual care. Methods One hundred T2D patients from general practices in the Netherlands with a BMI ≥ 27 kg/m2, treated with lifestyle advice only or lifestyle advice plus metformin, will be randomised to receive the FMD plus usual care or usual care only. Primary outcomes are HbA1c and T2D medication dosage. Secondary outcomes are anthropometrics, blood pressure, plasma lipid profiles, quality of life, treatment satisfaction, metabolomics, microbiome composition, MRI data including cardiac function, fat distribution and ectopic fat storage, cost-effectiveness, and feasibility in clinical practice. Discussion This study will establish whether monthly 5-day cycles of a FMD during a year improve metabolic parameters and/or reduce the need for medication in T2D. Furthermore, additional health benefits and the feasibility in clinical practice will be measured and a cost-effectiveness evaluation will be performed. Trial registration The trial was registered on ClinicalTrials.gov. Identifier: NCT03811587 . Registered 21th of January, 2019; retrospectively registered.