Early time-restricted carbohydrate consumption vs conventional dieting in type 2 diabetes: a randomised controlled trial

Aims/hypothesis Early time-restricted carbohydrate consumption (eTRC) is a novel dietary strategy that involves restricting carbohydrate-rich food intake to the morning and early afternoon to align with circadian variations in glucose tolerance. We examined the efficacy, feasibility and safety of eTRC in individuals with type 2 diabetes under free-living conditions. Methods In this randomised, parallel-arm, open label, controlled trial, participants with type 2 diabetes and overweight/obesity (age 67.2±7.9 years, 47.8% women, BMI 29.4±3.7 kg/m 2 , HbA 1c 49±5 mmol/mol [6.6±0.5%]) were randomised, using computer-generated random numbers, to a 12 week eTRC diet or a Mediterranean-style control diet with matched energy restriction and macronutrient distribution (50% carbohydrate, 30% fat and 20% protein). The primary outcome was the between-group difference in HbA 1c at 12 weeks. Body composition, 14 day flash glucose monitoring and food diary analysis were performed every 4 weeks. Mixed meal tolerance tests with mathematical beta cell function modelling were performed at baseline and after 12 weeks. Results Twelve (85.7%) participants in the eTRC arm and 11 (84.6%) participants in the control arm completed the study, achieving similar reductions in body weight and fat mass. The two groups experienced comparable improvements in HbA 1c (−3 [−6, −0.3] mmol/mol vs −4 [−6, −2] mmol/mol, corresponding to −0.2 [−0.5, 0]% and −0.3 [−0.5, −0.1]%, respectively, p =0.386), fasting plasma glucose, flash glucose monitoring-derived glucose variability and mixed meal tolerance test-derived glucose tolerance, insulin resistance, insulin clearance and plasma glucagon levels, without changes in model-derived beta cell function parameters, glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide and non-esterified fatty acid levels. The two diets similarly reduced liver function markers and triglyceride levels, being neutral on other cardiometabolic and safety variables. In exploratory analyses, diet-induced changes in body weight and glucometabolic variables were not related to the timing of carbohydrate intake. Conclusions/interpretation The proposed eTRC diet provides a feasible and effective alternative option for glucose and body weight management in individuals with type 2 diabetes, with no additional metabolic benefits compared with conventional dieting. Trial registration ClinicalTrials.gov NCT05713058 Funding This study was supported by the European Society for Clinical Nutrition and Metabolism (ESPEN) and the Italian Society of Diabetology (SID). Graphical Abstract