Introduction: Type 2 diabetes mellitus (T2DM) is a major cause of morbidity and mortality across the world. The importance of glycaemic control in T2DM is well-established and remains a key treatment target, as poor glycaemic control is associated with diabetes-related complications⁽¹⁾. Alongside HbA1c, best practice guidelines⁽²⁾ highlight the clinical significance of short-term measures of glycaemic variability to assess glycemia in those with T2DM. Long-term adherence to dietary and behavioural strategies to manage glycaemia is often poor, so novel approaches are warranted. It is well-known that circadian rhythms play a key role in human metabolism⁽³⁾. For example, glucose tolerance is typically optimal in the morning compared to later in the day. Time-restricted eating (TRE) – where energy intake is typically limited to <12 hours per day – may be a simple and effective dietary approach to the management of T2DM as it considers the importance of meal timing⁽⁴⁾. Research thus far suggests the metabolic benefits associated with TRE are driven by the position of the eating window and studies have shown that early-TRE may promote superior metabolic benefits in healthy individuals⁽⁵⁾. However, studies in those with T2DM are sparse.

Aims/hypothesis: To compare early versus late-TRE in adults with T2DM. We hypothesised that a daily 16-hour fast would lower mean 24-hour glucose concentration and improve other markers of glycaemic control, in individuals with T2DM. We hypothesised that these changes would be greater following early-TRE than late-TRE.

Methods: This study received a favourable ethical opinion from the University of Surrey Ethics Committee. Written informed consent was obtained prior to screening participants for eligibility for this 9-day cross-over, controlled eucaloric dietary intervention study. Eligible participants (n = 8) were fitted with continuous glucose monitors and allocated to group A or group B. All participants completed a 3-day control diet (eating window [EW] 7:00h to 19:00h), then Group A followed 3 days of early-TRE (EW 7:00h to 15:00h) while Group B commenced 3 days of late-TRE (EW 12:00h to 20:00h) before crossing over. All food (3 meals per day) consumed by participants during the study period was provided by the research team.

Results: Repeated measures ANOVA with post hoc tests using Bonferroni corrections were used to analyse measures of glycaemic control. Data are presented as mean ± SEM unless otherwise specified, with p<0.05 considered significant. Indices of glycaemic variability (CV and SD) were significantly lower in the late-TRE group compared to the control and early-TRE groups (CV, p<0.001 and p<0.001 respectively; SD, p = 0.007 and p = 0.003, respectively). A reduction in the 3-hour postprandial responses in the late-TRE group for meal 2 and meal 3 was observed, compared to the early-TRE group (p = 0.036 and p = 0.026, respectively). Late-TRE, but not early-TRE, increased time in glucose target range (3.9-10.0 mmol/L) – 78.4 ± 4.2 % in the late-TRE group compared to 68.9 ±4.4 % in the control group (p = 0.026) – Figure 1.

Conclusions/interpretation: Our data suggest that short-term late-TRE provides superior benefits to acute markers of glycaemic control compared with early-TRE in T2DM.