Effects of continuous calorie restriction versus time-restricted intermittent fasting on glycemic variability in individuals with type 2 diabetes: a randomized crossover trial

Moderate caloric restriction facilitates sustained weight control and reduces the incidence of type 2 diabetes, while meal timing and prolonged fasting may augment these advantages. Additionally, advancements in diabetes technology are improving glycemic control, by targeting Glycemic Variability (GV). However, dietary intervention studies on GV remain limited. We aimed to evaluate the changes in GV following a Continuous Calorie-restricted (CCR) Diet (reducing daily energy intake by 500 kcal/day) versus Time Restricted Intermittent Fasting (TRIF) (Calorie-matched as CCR but with restricted feeding window and only two meals) among individuals with type 2 diabetes. An interventional clinical trial with a cross-over design (CTRI/2022/07/044356) was done with 51 participants between 25 and 55 years of age, with type 2 diabetes of ≤ 5 years, taking only Metformin or drug-naive, and HbA1c between 6.5 and 8% (48-64mmol/mol). A Continuous Glucose Monitor (CGM) by Abbot was used to evaluate the Time in Range (TIR), and other GV metrics at the end of both interventions. The carry-over and treatment effects at the end of the two interventions were significantly different between the groups, with better outcomes at the end of the CCR. TIR was significantly greater following CCR (92.4 ± 5%) than following TRIF (81.4 ± 6.5%) ( p = 0.001). Whereas TAR and TBR were significantly lower after CCR intervention, with a TAR of 4.6 ± 4.7% and a TBR of 2.9 ± 3.2% than after TRIF with values of 10.9 ± 8.4% and 7.7 ± 6.1% and p-value of 0.001 and 0.009, respectively. Calorie restriction is more effective in managing GV than time restricted feeding. Calorie restriction and careful planning of macro-nutrient distribution can emerge as a useful tool for planning dietary guidelines for individuals with type 2 diabetes.