Effect of time restricted eating versus current practice in dietetics on glycaemic control and cardio-metabolic outcomes in individuals at risk of developing type 2 diabetes: Protocol for a multi-centre, parallel group, non-inferiority, randomised controlled trial

Background: Time restricted eating (TRE) is a dietary strategy that may improve metabolic health. However, no studies have compared TRE with current practice (CP) in dietetics. Hypothesis: TRE will not be inferior to CP to improve glycaemic control in individuals at risk of type 2 diabetes (T2D). Methods: This parallel group, randomised, non-inferiority, controlled trial randomised 247 participants by site and glycated haemoglobin (HbA1c) into TRE or CP (1:1) for 12 months. Participants were aged 35–70 years, with a body mass index (BMI) >25 but <45 kg/m², and score ≥15 on the Australian type 2 diabetes risk (AUSDRISK) assessment, without a diagnosis of T2D. Study visits were balanced between groups and all participants received five consultations at 0, 0.5, 1, 2 and 3 months. TRE followed a self-selected 9 h eating window (≥0600 and ≤1900), whereas CP followed Australian dietary guidelines. Outcomes: The primary endpoint is the estimate of group mean difference (TRE vs CP) of HbA1c at 4 months in a covariate linear regression adjusting for stratification factors and sex. Secondary efficacy outcomes at 4 and 12 months are changes in fasting glucose, fasting insulin, HOMA-IR and nocturnal glucose by continuous glucose monitor incremental area under the curve and change in HbA1c at 12 months. Other endpoints are exploratory and will not be adjusted for multiplicity. Conclusions: We will determine whether TRE is an alternate strategy to current practice in dietetics to improve glucose control. Trial registration: NCT04762251; 21 Feb 2021.