Restricted Eating Time in the Treatment of Type 2 Diabetes

The overall aim of the present study is to investigate the effectiveness of implementing a 1-year time-restricted eating (TRE)-based intervention on glycaemic control, body weight and composition, cardiometabolic risk factors, and behaviour in individuals with overweight/obesity and type 2 diabetes (T2D).

In people with type 2 diabetes (T2D), weight loss is associated with improved glycaemic control and markers of cardiometabolic function as well as reduced use of antidiabetic medicine. Beyond pharmacological treatments, current strategies to reduce body weight and improve glycaemia include energy-restricted diets and increased physical activity.

Lifestyle interventions are complex, affecting many aspects of peoples' daily life. Dietary restrictions often result in rapid weight loss but the weight is gradually regained by many. Barriers to implement and maintain dietary changes include relapse of old habits and lack of knowledge, support, and insights into the type and amount of foods eaten. Previous lifestyle interventions targeting weight loss in T2D show efficacy for improving markers of metabolic and cardiovascular risk, including body weight and glycaemia during the intervention, but weight regain is often present. One reason may be that the intervention is not modified according to the needs of the target group. Often, weight loss interventions are shaped by a 'one size fits all' approach where both individual capabilities and motivation as well as social and contextual factors are more or less ignored. A user-based design could facilitate enrolment of participants and promote implementation and maintenance of the intervention among participants.

Intermittent fasting regimens have been suggested as efficient strategies for improving cardiometabolic health to a greater extent than can be attributed to the reduction in energy intake alone. TRE limits the time available for food intake to typically 8-10 hours/day without other dietary restrictions and has been put forward as a novel, acceptable, and safe strategy that has shown promising effects on body weight, glucose metabolism, appetite, and cardiometabolic health in individuals at high risk of T2D.

Although it has been suggested that TRE is a safe and feasible intervention, the longer-term effectiveness of TRE on glycaemic control and weight loss in individuals with T2D is unknown alongside the long-term acceptability and sustainability. Additionally, potential social and contextual challenges associated with integration of TRE into ordinary daily life structure and routines call for new approaches to support the individual in implementing and maintaining the strategy.

Overall, the RESET2 study consists of three phases; 1) Need assessment, 2) Pilot study, and 3) RCT. The aim of the present study (RCT) is to investigate the effectiveness of implementing a 1-year TRE-based intervention in individuals with overweight/obesity and T2D. Participants will attend 6 visits at Steno Diabetes Center Copenhagen (SDCC): Visit 0 (screening), Visit 1 (baseline, minimum 10 days after screening), Visit 2 (10 days prior to visit 3), Visit 3 \[3 months (12 weeks) after baseline\], Visit 4 (10 days prior to visit 5), Visit 5 \[12 months (52 weeks) after baseline\].

The specific objectives are:

1. To investigate the effect of a 1-year TRE intervention on changes in glycaemic control (HbA1c) in individuals with overweight/obesity and T2D.
2. To investigate the effects of a 1-year TRE intervention on changes in body weight, fat mass, continuous glucose monitoring (CGM) recorded time in range (TIR 3.9-10.0 mmol/l), and use of antidiabetic medication in individuals with overweight/obesity and T2D.
3. To describe changes in cardiometabolic risk factors (including fat-free mass, blood lipids, markers of kidney and liver function and inflammation, hormones involved in glucose metabolism and appetite control, liver fat, blood pressure, waist- and hip circumference), time below range (TBR), time above range (TAB), cognition, food preferences and reward, dim light melatonin onset (DLMO), and patient-reported outcomes including self-rated health, physical activity, well-being, diabetes distress, depression, food intake, and sleep quality.
4. To investigate the effects of a 3-month TRE intervention on changes in brain insulin sensitivity (sub-study).
5. To describe the extent to which the intervention was conducted as planned (visits, conversations, phone calls, peer support activities).
6. To describe the extent to which participants participated in support-related activities.
7. To explore participants' experiences with following TRE throughout a year including how they managed to keep their eating window and how the supporting activities and individualized approach worked for them (sub-population).
8. To explore the results from objectives 1-7 in relation to the extent the participants adhered to eating windows.

Eligibility Criteria:
Inclusion Criteria:

* Age: ≥18 years
* Overweight or obesity (BMI ≥25 kg/m2)
* T2D with HbA1c\>53 mmol/mol
* Habitual eating window ≥12 h/day (incl. foods/snacks and energy-containing beverages)

Exclusion Criteria:

* Bariatric surgery or planned bariatric surgery within study duration
* Use of fast acting insulin and combination insulin products
* Habitual CGM use
* A wish to adhere to Ramadan
* For women: current/planned pregnancy or lactation
* Alcohol or drug abuse (judged by investigator) or treatment with disulfiram
* Severe hypoglycaemia within last year (Severe hypoglycaemia, as defined by the American Diabetes Association (ADA), denotes severe cognitive impairment requiring external assistance for recovery)
* Inability to understand written and oral information in Danish
* Unable or unwilling to adhere to TRE; for instance, due to competing medical conditions.
* Medical condition which, based on investigators assessment, challenges participation including but not limited to severe heart, vascular or lung disease, cancer, chemotherapy, psychiatric, gastrointestinal, rheumatic, or endocrine diseases etc.
* Concomitant participation in other intervention study
* Inability to perform neuropsychological tests (e.g., severe vision and hearing impairment that can-not be improved with aids such as glasses and hearing aids, or language barrier.)

Exclusion criteria for the sub-study:

* Magnetic resonance imaging (MRI) contraindications based on the MR department's exclusion criteria including pacemaker or other implanted electronic devices, implanted metal objects not compatible to MRI scanning and severe claustrophobia
* Participants who do not wish to be informed about accidental findings by MR.