Background: Time-restricted feeding can improve insulin sensitivity, and increase fat oxidation in people with prediabetes independent of weight loss. It may also help people to lose weight. However, it has not been tested in people with type 2 diabetes.

Plan of investigation: Participants meeting the eligibility criteria will be randomized to the TRF arm or the continuous eating arm. Both arms with be given a prescribed dietary plan to help them lose 5% of body weight. In the TRF they will permitted to eat between midday and 6pm. In the continuous eating arm they will be allowed to eat between 8am and 11pm. Participants will attend the nutrition clinic every two weeks to be weighed and be given personalized support to help them follow their assigned diet. Prior to starting the diets outcome measures will be taken: Glycaemia will be measured by a glucose tolerance test, and 7-day continuous glucose monitoring. HbA1c will be taken from fasting blood sample. In addition, the fasting sample will be taken for measurement of insulin, lipid profile and inflammatory markers. We will also use questionnaires to assess quality of life, a 3-day food diary to assess compliance to diet especially meal timings. Capillary ketones will also be used to assess whether compliance to the assigned fasting period. Outcome measures will also be taken during 7 days of the second month, and then the final seven days of the last month on the diet. The primary outcome is HbA1c.

Experimental Design

12-week parallel randomised control trial

Recruitment

We will recruit via advertisements outside Dasman using social media and local ads in addition to screening of Dasman Registry for any potential participants. Opportunistic recruitment will also occur by DDI dietitians. Following telephone screening to ensure the potential participant meets initial screening criteria we will carry out a medical screening to ensure the person can take part.

Environment All screening, dietary counselling visits, and placement of the CGM will take place at the Dasman Diabetes Institute (DDI). The institute has extensive space for interventional studies, including screening rooms, body composition assessment and clinical rooms for placement of the CGM monitor.

STUDY INTERVENTIONS

For both groups all participants will be guided towards a 5% weight loss based on individualised energy requirements. The difference will be the hours during which the participants consume their required calories.

• Time restricted feeding group: Will consume their calories between 12pm and 6pm.
• Continuous energy restriction group: Will consume their calories between 8am and 11pm.

Participants will be guided towards their weight loss during one-to-one visits at baseline and every 2 weeks for 12 weeks.

Procedures

• At baseline and follow-up all participants will undergo an oral glucose tolerance test.
• A blood sample will also be taken for HbA1c, lipid profile, fasting insulin, inflammatory factors and a sample for Biobank. The biobank sample will be stored to enable us, with other researchers at DDI to understand the heterogeneity of type 2 diabetes; whether certain people respond to dietary interventions based on their genetic, epigenetic or metabolomic background; and ultimately will help guide clinical care.
• Participants will wear Flash Glucose monitoring or other continuous glucose monitoring device to measure their 24-hour blood glucose concentrations during the seven days preceding the start of the dietary intervention, seven days of the second month, and the final seven days of the third month.
• Participants will also measure their capillary ketones during the first three days of the first month, three days of the second month, and final three days of the third month.
• Medication changes: prandial medications (insulin or sulphonylurea) will be altered to the timing of meal intake. Any reduction in medication due to changes in glucose will be carried out by the patient's doctor.
• A quality of life questionnaire: PAID.
• A 3 day food diary with meal times to check compliance.

Statistical Methods

This is a pilot study. We will recruit 25 people per group. This is based on recommendations for sample sizes for feasibility and pilot studies.

Inclusion Criteria:

• Must agree to follow time restricted feeding protocol if randomized to the TRF arm.
• Age 21-65 years
• T2DM with any diabetes medication
• BMI of 25-45 kg/m2
• Wake up at a regular time between 5-8 am
• Able to provide informed consent.

Exclusion Criteria:

• Weight loss of more than 5 kg within the past 6 months
• HbA1c of <6·5% and >12%
• Serious current or recent illness including cancer or severe or unstable heart failure.
• Participation in another clinical research trial.
• Current treatment with anti-obesity drugs.
• Substance abuse
• Learning difficulties
• Presence of an eating disorder
• Purging behaviour
• Pregnancy or consideration of pregnancy
• Hospital admission for depression or use of antipsychotic drugs.
• Regularly eat within a <9-hour period each day
• Inability or unwillingness of individual or legal guardian/representative to give written informed consent.