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Trial registered on ANZCTR


Registration number
ACTRN12624001281583
Ethics application status
Approved
Date submitted
3/10/2024
Date registered
22/10/2024
Date last updated
15/12/2024
Date data sharing statement initially provided
22/10/2024
Type of registration
Prospectively registered

Titles & IDs
Public title
GluCoast: Dietary strategies for glucose control in type 2 diabetes
Scientific title
Effect of partial diet replacement or time-restricted eating on tight time-in-range for people with type 2 diabetes: a randomised crossover trial
Secondary ID [1] 313054 0
None
Universal Trial Number (UTN)
U1111-1307-9673
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Type 2 diabetes 335280 0
Overweight 335281 0
Obesity 335468 0
Condition category
Condition code
Metabolic and Endocrine 331855 331855 0 0
Diabetes
Diet and Nutrition 331856 331856 0 0
Obesity

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
This study consists of two separate dietary interventions (time-restricted eating and partial diet replacement), each lasting two weeks. These will be preceded by a two-week period of baseline monitoring and separated by a minimum two-week washout period. During each of the baseline monitoring and washout periods, participants will be asked to adhere to their usual eating habits, with no further lifestyle advice provided. Participants will wear a continuous glucose monitoring (CGM) sensor to assess glycaemic control during the two-week baseline monitoring period and each of the two-week dietary interventions. Throughout the duration of the study, participants will be asked to maintain their usual physical activity levels and will continue to receive usual care through their general practice.

Interventions will be delivered by a member of the research team via five individual, face-to-face study visits held at baseline and before and after each two-week dietary intervention. Participants will also have an initial Zoom/phone call/in-person visit to assess eligibility and provide study information. ‘Check ins’ and additional support (if required) will be available via text, phone call, or email between visits. The expected duration of participation is eight weeks (longer if the participant requires additional time between visits and/or a washout period longer than two weeks). Study visits will be held in a local hospital/clinical/office space and are expected to last 30–60 minutes each. Study visits will include (as appropriate) administering the interventions, providing participants with required resources (e.g. meal replacement products; adherence checklists); application/removal of CGM sensors; data collection (e.g. weight; blood pressure; questionnaires; qualitative interviews); and post-intervention review of adherence checklists, diet records, and reported side effects. After completing both interventions, participants will be offered an optional in-person review of their continuous glucose monitoring results and (if appropriate) self-reported dietary intakes. This may include individualised nutrition education and advice. This review may take place during the final study visit or at a later date.

Time-restricted eating intervention:
In the time-restricted eating intervention, participants will be asked to maintain their usual food choices but to restrict their intake of all food and energy-containing beverages (e.g., tea/coffee with milk) to a self-selected 9-hour window ending no later than 7:00pm. No further dietary advice (e.g. food choice, portion size, diet quality, or meal timing within window) will be provided. Participants will be asked to adhere to the same self-selected eating window on as many days as possible during the entire two-week time-restricted eating intervention. For example, participants may choose to consume all food and energy-containing beverages between 10:00am and 7:00pm each day for two weeks, or between 8:45am and 5:45pm each day for two weeks. Participants may freely consume non-nutritive beverages (i.e., water, plain tea, black coffee, and zero-energy/diet drinks) throughout the intervention. Intervention adherence will be assessed using a three-day diet record (on paper or app-based) and a daily adherence checklist (including the time of the first and last eating occasion). These will be completed by participants and checked for accuracy at the next study visit.

Partial diet replacement intervention:
In the partial diet replacement intervention, participants will be asked to maintain their usual food choices, except for replacing any two main meals per day with the meal replacement products we provide. Participants will be asked to adhere to this approach on as many days as possible throughout the entire two-week partial diet replacement intervention, but the timing of meal/meal replacement consumption needn’t be the same each day. For example, participants might choose to consume meal replacements at breakfast and lunch with a ‘real food’ dinner on Day 1, followed by meal replacements at breakfast and dinner with a ‘real food’ lunch on Day 2. Meal replacement products (Cambridge Weight Plan Ltd., Corby, Northants, UK) will be provided free of charge, and a variety of options (e.g., shakes, soups, bars, porridges, and meals) and flavours will be available. Each meal replacement product has an energy content of approximately 850 kJ (~200 kcal).

Participants may freely consume non-nutritive beverages (i.e., water, plain tea, black coffee, and zero-energy/diet drinks) throughout the intervention. Intervention adherence will be assessed using a three-day diet record (on paper or app-based) and a daily adherence checklist (including the number of meal replacements and real-food meals consumed). These will be completed by participants and checked for accuracy at the next study visit.
Intervention code [1] 329609 0
Lifestyle
Comparator / control treatment
As this is a randomised crossover trial, each participant acts as their own comparator/control. The two-week baseline monitoring period will allow us to examine changes in measures including CGM glycaemic control and dietary intake.
Control group
Active

Outcomes
Primary outcome [1] 339472 0
24-hour time in tight range (TITR)
Timepoint [1] 339472 0
Baseline and during each dietary intervention
Primary outcome [2] 339473 0
Acceptability of the dietary intervention
Timepoint [2] 339473 0
Post-completion of each dietary intervention
Secondary outcome [1] 440128 0
Body weight (kg)
Timepoint [1] 440128 0
Baseline and pre- and post-completion of each dietary intervention
Secondary outcome [2] 440129 0
Systolic and diastolic blood pressure
Timepoint [2] 440129 0
Baseline and pre- and post-completion of each dietary intervention
Secondary outcome [3] 440130 0
Body fat percentage
Timepoint [3] 440130 0
Baseline and pre- and post-completion of each dietary intervention
Secondary outcome [4] 440131 0
Body Mass Index (BMI)
Timepoint [4] 440131 0
Baseline and pre- and post-completion of each dietary intervention
Secondary outcome [5] 440132 0
24-hour time in range (TIR)
Timepoint [5] 440132 0
Baseline and during each dietary intervention
Secondary outcome [6] 440133 0
24-hour mean blood glucose
Timepoint [6] 440133 0
Baseline and during each dietary intervention
Secondary outcome [7] 440134 0
Glycaemic variability
Timepoint [7] 440134 0
Baseline and during each dietary intervention
Secondary outcome [8] 440135 0
Glycaemic variability
Timepoint [8] 440135 0
Baseline and during each dietary intervention
Secondary outcome [9] 440136 0
Glycaemic variability
Timepoint [9] 440136 0
Baseline and during each dietary intervention
Secondary outcome [10] 440137 0
Time above glycaemic range (TBR)
Timepoint [10] 440137 0
Baseline and during each dietary intervention
Secondary outcome [11] 440138 0
Time below range (TBR)
Timepoint [11] 440138 0
Baseline and during each dietary intervention
Secondary outcome [12] 440139 0
Measures of nocturnal glycaemic control
Timepoint [12] 440139 0
Baseline and during each dietary intervention
Secondary outcome [13] 440140 0
Measures of daytime glycaemic control
Timepoint [13] 440140 0
Baseline and during each dietary intervention
Secondary outcome [14] 440141 0
Dietary intake (energy and nutrient intake)
Timepoint [14] 440141 0
Baseline and during each dietary intervention
Secondary outcome [15] 440142 0
Occurrence of side effects
Timepoint [15] 440142 0
During each dietary intervention
Secondary outcome [16] 440143 0
Physical activity level
Timepoint [16] 440143 0
Baseline and pre- and post-completion of each dietary intervention
Secondary outcome [17] 440144 0
Diet satisfaction
Timepoint [17] 440144 0
Baseline and pre- and post-completion each dietary intervention
Secondary outcome [18] 440145 0
Quality of life
Timepoint [18] 440145 0
Baseline and pre- and post-completion each dietary intervention
Secondary outcome [19] 440146 0
Adherence to the dietary intervention
Timepoint [19] 440146 0
During each dietary intervention

Eligibility
Key inclusion criteria
Participants will be aged 18–80 years, with overweight or obesity and medically-diagnosed type 2 diabetes. Participants must be willing to participate in both dietary interventions for a period of two weeks each (including consuming meal replacement products which may contain milk/dairy and/or gluten) and be willing to wear only a blinded CGM sensor (i.e., not wear a CGM for personal use) for up to six weeks in total.
Minimum age
18 Years
Maximum age
80 Years
Sex
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
• Not weight stable (i.e., >5 kg change in body weight in the previous 3 months)
• Doctor-prescribed change to glucose-lowering or anti-obesity medications in the last 3 months
• Current insulin use
• Previous weight loss surgery
• Night shift worker (i.e., working >3 hours between 10pm and 5am at least once per week in the previous 3 months or over the study duration)
• Myocardial infarction in the last three months
• Currently receiving cancer treatment
• Diagnosed or self-reported eating disorder
• Pregnancy or lactation (current or planned over the study duration).

Eligibility may also be affected by prescribed medications which increase the risk of hypoglycaemia (e.g., sulfonylureas) or which must be taken with food in the early morning or late evening (i.e., outside the time-restricted eating window). Food allergies or intolerances may also limit the variety of meal replacement products suitable for some individuals. These issues will be discussed with participants and the appropriate health professional on a case-by-case basis.

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Central randomisation by computer (built into REDCap online portal).

The evening before each participant attends their first intervention session the next sequential randomization will be revealed and assigned. Participants will not be notified of which intervention they are completing until they arrive at their first session. By process of elimination however, participants will know their second intervention as soon as they begin the first intervention session.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a computerised sequence generation, no stratification. The randomisation sequence will be generated using Stata software and concealed electronically.
Masking / blinding
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
We intend to recruit a sample of 30 participants as we consider this to be a feasible and recruitment target. Specifying a two-sided alpha level of 0.05 (Type I error) and assuming both approximately equal standard deviations in each intervention and a within-person correlation of 0.5, a total sample size of n=30 will ensure 80% power to detect a 0.53 standard deviation difference in the primary quantitative outcome (24-hour TITR) between the partial diet replacement and time-restricted eating interventions. Furthermore, n=30 will provide 90% power to detect a 0.62 standard deviation difference. With respect to the assessment of intervention acceptability, n=30 is a large sample size for qualitative analysis. We expect a sample this size to provide ample data to sufficiently address the qualitative aim of the proposed study.

Statistical analyses will be conducted according to intention-to-treat principles. Linear mixed effects models will be used to investigate the difference in the primary outcome (24-hour TITR) between the two interventions. This regression approach will incorporate participant as a random effect and adjust for both baseline 24-hour TITR and randomisation order. Stata software version 18.0 will be used for all statistical analyses with two-sided p<0.05 considered statistically significant.

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
1/01/2025
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
31/10/2025
Actual
Sample size
Target
30
Accrual to date
Final
Recruitment outside Australia
Country [1] 26575 0
New Zealand
State/province [1] 26575 0
West Coast (South Island)

Funding & Sponsors
Funding source category [1] 317496 0
University
Name [1] 317496 0
Edgar Diabetes and Obesity Research Centre of the University of Otago, Aotearoa New Zealand
Country [1] 317496 0
New Zealand
Primary sponsor type
Individual
Name
Dr Andrew Reynolds, University of Otago, Aotearoa New Zealand
Address
Country
New Zealand
Secondary sponsor category [1] 319850 0
None
Name [1] 319850 0
Address [1] 319850 0
Country [1] 319850 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 316207 0
Northern B Health and Disability Ethics Committee 
Ethics committee address [1] 316207 0
Ethics committee country [1] 316207 0
New Zealand
Date submitted for ethics approval [1] 316207 0
18/09/2024
Approval date [1] 316207 0
14/11/2024
Ethics approval number [1] 316207 0
2024 EXP 20642

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 137146 0
Dr Andrew Reynolds
Address 137146 0
Department of Medicine, University of Otago, PO Box 56, Dunedin Otago 9012, New Zealand
Country 137146 0
New Zealand
Phone 137146 0
+64 279565826
Fax 137146 0
Email 137146 0
andrew.reynolds@otago.ac.nz
Contact person for public queries
Name 137147 0
Kate Campbell
Address 137147 0
Department of Medicine, University of Otago, PO Box 56, Dunedin Otago 9012, New Zealand
Country 137147 0
New Zealand
Phone 137147 0
+64 212791490
Fax 137147 0
Email 137147 0
kate.campbell@postgrad.otago.ac.nz
Contact person for scientific queries
Name 137148 0
Andrew Reynolds
Address 137148 0
Department of Medicine, University of Otago, PO Box 56, Dunedin Otago 9012, New Zealand
Country 137148 0
New Zealand
Phone 137148 0
+64 279565826
Fax 137148 0
Email 137148 0
andrew.reynolds@otago.ac.nz

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.