Background: Intermittent energy restriction (IER) diets, consisting of periods with restricted food intake alternated with periods of unrestricted food intake, have gained popularity. For patients with type 2 diabetes mellitus (T2D) these diets might help improve health parameters.

Methods: We conducted a systematic review of the effects of IER in patients with T2D regarding markers of metabolic control, anti-diabetic medication dosage and quality of life. Two investigators independently selected studies, extracted data and assessed risk of bias using the Cochrane Collaboration’s tool.

Results: Twelve studies were included. There was wide heterogeneity in these studies due to different dietary interventions, study designs and study durations. A qualitative synthesis of the results was performed. Five out of ten studies that reported HbA1c found a significant decline after IER, which ranged from -0.3% to -2.3%. Four out of ten studies found a significant decline in glucose levels, which ranged from -0.78 to -3.01 mmol/L. Four studies described a reduction in anti-diabetic medication use after IER (no statistical tests were performed). Six out of ten studies that reported weight found a significant decline. Effects found on lipid levels, blood pressure, waist circumference and body fat were limited. Treatment satisfaction or quality of life were scarcely measured. Only four studies had a long term follow-up (≥1 year after the intervention). The improvements on HbA1c or weight were generally not maintained.

Discussion: Limited evidence is available on IER interventions in patients with T2D. The results from this review suggest that IER can potentially improve glucose regulation and reduce weight in patients with T2D. There are also some indications that IER could be beneficial to reduce anti-diabetic medication use in the short term. For future research, we advise longer intervention periods and to use anti-diabetic medication as an outcome measure.