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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Nocturnal blood glucose responses to potato-based mixed evening meals
Scientific title
The blood glucose response to a potato-based mixed evening meal in individuals with Type II Diabetes
Secondary ID [1] 293897 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Type II Diabetes Mellitus 306368 0
Condition category
Condition code
Diet and Nutrition 305456 305456 0 0
Other diet and nutrition disorders
Metabolic and Endocrine 306284 306284 0 0

Study type
Description of intervention(s) / exposure
The blood glucose response of all participants who consume four mixed meals including a potato element (boiled, baked or boiled then cooled) or basmati rice (control) on four occasions separated by a minimum of 7 days will be measured.
Overview of design:
Twenty four participants with type 2 diabetes mellitus (T2DM), male and female, body mass index (BMI) 22 – 40 kg/m2 and aged 35 – 75 years old, will be included in a randomised cross-over study. All participants will complete all four conditions in random order with a minimum 7-day wash-out period between trials. Four evening meal conditions will be tested including dinner of meat and vegetables with either BOILED, BAKED, BOILED THEN COOLED potato or a CONTROL of basmati rice. All meals will be matched for energy and macronutrient composition. Daily diet composition will be 50% carbohydrate, 30% fat and 20% protein. Each meal will be the same composition as the overall daily diet composition. Energy distribution over the day will be 25% of total energy intake (TEI) at breakfast, 30% TEI at lunch and 45% TEI at dinner. Potato and rice will make up the carbohydrate content of the evening meal.
Participants will receive a Participant Information Letter outlining study procedures and a handbook to log physical activity and sleep during the intervention. Checklists for standardised meals to be consumed, space to record dietary intake and an outline of scheduled laboratory visits will be included in a handbook provided.
Experimental conditions will take place within the Daniel Mannix Building at Australian Catholic University. Participants will attend the laboratory on a minimum of 18 occasions as outlined below:
Visit 1: Forms. Study procedures explained prior to obtaining written consent.
Visit 2: Baseline measurements. Resting metabolic rate (RMR), Dual-Energy X-Ray Absorptiometry (DXA), blood pressure and anthropometric measurements.
Visits 3, 6, 9 & 12 (Day - 3): Monitors and provision of standardised meals. A continuous glucose monitor (CGM) and three activity monitors will be inserted/put on. Participants will collect their standardised meals for consumption the day before the trial day (to be consumed on Day 0).
Visits 4, 7, 10 & 13 (Day 1): Trial days. Participant will attend the laboratory at 7am. A fasted blood sample will be collected at this time and breakfast and lunch will be provided for participants to consume in their “free living” environment that day. Participants will return to the lab that evening to have a cannula inserted to collect blood samples following consumption of one of the four dinner meals. These four visits require participants to attend in the morning (for the fasted blood sample) and then they are free to leave but will be required to return for the evening. Therefore, there are four additional occasions participants will need to attend the lab but are part of the same Trial day (i.e. am and pm visits).
Visits 5, 8, 11 & 14 (Day 2): Blood sample and monitor removal. Participants will return to the lab for collection of a fasted blood sample and removal of monitors.

Following a minimum 7 day “washout period”, participants will re-attend the lab and repeat visits 3 – 5 until all four conditions are completed.

Description of study procedures:
RMR: Participants will lie down in a quiet, dim-lit room for 25 min where RMR will be measured using an automated gas analyser. A hood (clear) will be placed over the participants head and connected to the gas analyser. The 25 minutes includes a 10 minute rest period, followed by a 15 minute period of data collection.

DXA: Participants will undergo a whole body DXA scan. Participants will lay supine on the scanning bed for the duration of the 15 minute scan. There will be one to two scans depending on the body shape of the participant. The machine uses small doses (<1% of the yearly radiation dose) of radiation to estimate tissue density. The total effective dose of radiation has been calculated for this machine and the scans for this study by a Medical Physicist. This test requires the participant be fasted with no food, fluid or exercise/activity prior to the test. Light clothing with no metal items (i.e. zips, domes, clips, underwire etc.) should be worn (gowns are available if need be) and all jewellery must be removed. All measures will be taken by trained researchers who hold radiation licences with Victorian Government and comply to the Code of Practice set out by the Australian Radiation Protection and Nuclear Safety Agency.

Blood pressure: blood pressure (BP) will be measured via an automated BP machine. Three measures will be taken, a minimum of 1 minute apart. Each measure is approximately 3 minutes in duration. The participant will have a cuff applied to the upper portion of the arm. This will inflate and tighten around the arm and then slowly release.

Three-day dietary record: Participants will asked to record their habitual dietary intake on the three days preceding the first experimental trial. They will be asked to mimic this as closely as possible prior to the three subsequent trials.

Continuous blood glucose monitoring (CGM): Participants will be required to wear the minimally invasive Medtronic iPro2 blood glucose monitoring system for the four day period prior to all four trials, each trial day and the following morning. The monitor is the size of a 50 cent piece and the associated sensor inserted rather painlessly into the subcutaneous tissue of the lower back.

Physical activity and sleep monitors: To assess physical activity and sleep, participants will be fitted with an inclinometer (ActivPAL3TM) worn on the thigh, an ActiGraph accelerometer worn around the waist, and a SenseWear armband worn on the triceps muscle, to be worn for the four day period prior to all four trials, each trial day and the following morning.

Blood sampling: Eight samples will be collected during each of the four trial periods (32 samples in total). The total volume collected across the minimum 8 week period will be 192 mL.
Intervention code [1] 300170 0
Treatment: Other
Comparator / control treatment
Every participant will consume one meal containing basmati rice (control) instead of potato (test food) as one of the four conditions. All other variables/measures will remain the same.
Control group

Primary outcome [1] 304601 0
Postprandial glycemic response (net incremental area under the curve iAUC for glucose following the evening meal)
Timepoint [1] 304601 0
Blood sampling will take place prior to dinner consumption (5:00 PM) and 30, 60, 90, 120 min after the meal is consumed on the Trial Day.
Primary outcome [2] 304672 0
Postprandial insulin response (net incremental area under the curve iAUC for insulin) following the evening meal.
Timepoint [2] 304672 0
Blood sampling to measure postprandial glycemic response will take place prior to dinner consumption (5:00 PM) and 30, 60, 90, 120 min after the meal is consumed on the Trial day
Secondary outcome [1] 342515 0
24 hour blood glucose response area under the curve
Timepoint [1] 342515 0
Blood glucose will be continuously measured for the trial day and overnight using continuous glucose monitors (CGMs) following consumption of the trial day dinner meal until they are removed the following morning.
Secondary outcome [2] 342731 0
Ghrelin (appetite hormone)
Timepoint [2] 342731 0
A fasting blood sample will be obtained at 7:00 am on the morning of the trial day (Day 0). Blood sampling will take place prior to dinner consumption (5:00 PM) and 30, 60, 90, 120 min after the meal is consumed on the Trial day. Participants will return the following morning to obtain a fasted blood sample at 7:00 am.
Secondary outcome [3] 342732 0
Subjective measure of appetite and satiety (composite measure) via at 100mm visual analogue scale to indicate feelings of hunger/satiety.
Timepoint [3] 342732 0
Participants will complete electronically administered questionnaires on the trial day in the morning prior to breakfast at 7:15 am, before dinner at 5:30 pm, after dinner at 8:00 pm and on the morning following the trial day (Day 1) prior to breakfast at 7:15 am.
Secondary outcome [4] 344737 0
Daily energy expenditure via Sensewear arm bands
Timepoint [4] 344737 0
Worn throughout all trials from Day -3 through to Day 2.
Secondary outcome [5] 344738 0
Physical activity and sedentary patterns via Activpal/Actigraph monitors
Timepoint [5] 344738 0
Worn for each trial from Day -3 to Day 2.
Secondary outcome [6] 352889 0
Nocturnal blood glucose area under the curve
Timepoint [6] 352889 0
Blood glucose will be continuously measured overnight using continuous glucose monitors (CGMs) following consumption of the trial day dinner meal until they are removed the following morning.

Key inclusion criteria
Diagnosed Type II Diabetes for greater than 3 months, diet or metformin controlled.
Aged 35-75 y
BMI: 22-40 kg/m2
Sedentary in terms of structured and incidental physical activity and occupation (defined as less than 150 min/week moderate-intensity exercise for more than 3 months and sitting for more than 5 hours per day).
Minimum age
35 Years
Maximum age
75 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Major or chronic illness that impairs mobility or eating/digestion; previous bariatric surgery; smokers; individuals with strict dietary intake regimes that prevent them from consuming standardised meals and/or potato meals; individuals who have not been weight stable for the last 3 months. Pre/perimenopausal women; cigarette smokers; taking insulin or other hypoglycemic agents other than metformin.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation will be concealed as the study personnel are not aware of the randomization procedure. The randomization is administrated by a central administration site.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomization using a randomization table created by computer software (i.e. computerized sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Data from the four conditions will be analysed using Generalised Linear Mixed Models, with baseline measures of dietary intake, body fatness, physical activity etc. as covariates. Statistical significance will be set at p<0.05. All data will be represented as mean ± SD. Statistical analysis will be undertaken using SPSS (Version 22 for Windows, SPSS Inc, Chicago, IL).

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment postcode(s) [1] 18701 0
3065 - Fitzroy

Funding & Sponsors
Funding source category [1] 298519 0
Commercial sector/Industry
Name [1] 298519 0
Alliance for Potato Research and Education (APRE)
Address [1] 298519 0
PO Box 803312
Chicago, Illinois
Country [1] 298519 0
United States of America
Primary sponsor type
Dr Brooke Devlin
Exercise and Nutrition Research Program
Mary MacKillop Institute for Health Research
Level 5, 215 Spring Street, Melbourne, VIC 300
Melbourne, VIC 3000
Secondary sponsor category [1] 297667 0
Name [1] 297667 0
Prof John Hawley
Address [1] 297667 0
Exercise and Nutrition Research Program
Mary MacKillop Institute for Health Research
Level 5, 215 Spring Street, Melbourne, VIC 300
Melbourne, VIC 3000
Country [1] 297667 0

Ethics approval
Ethics application status
Ethics committee name [1] 299497 0
Australian Catholic University Human Research Ethics Committee
Ethics committee address [1] 299497 0
Research Services
Australian Catholic University
Melbourne Campus
Locked Bag 4115
Ethics committee country [1] 299497 0
Date submitted for ethics approval [1] 299497 0
Approval date [1] 299497 0
Ethics approval number [1] 299497 0

Brief summary
The purpose of the present study is to investigate the impact of potato consumption on postprandial and nocturnal glycemic response and postprandial insulin response when consumed as balanced mixed meal in a real-word setting in individuals with T2DM. Additionally, different cooking methods of potatoes will be explored (baked, boiled and boiled then cooled) and compared to brown rice of equal carbohydrate content (control).

We hypothesize ingestion of potato as part of a mixed evening meal will not result in any greater postprandial or nocturnal glycemic response or postprandial insulin response to an isoenergetic, macronutrient-matched control test meal due to the diurnal fluctuations in glucose regulation. Additionally, we hypothesize pre-cooking then cooling potato before consumption will lower the postprandial glycemic response of potato as part of a mixed evening meal.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 80618 0
Dr Brooke Devlin
Address 80618 0
Mary MacKillop Institute for Health Research
215 Spring St
Country 80618 0
Phone 80618 0
+61 3 9230 8052
Fax 80618 0
Email 80618 0
Contact person for public queries
Name 80619 0
Dr Brooke Devlin
Address 80619 0
Mary MacKillop Institute for Health Research
215 Spring St
Country 80619 0
Phone 80619 0
+61 3 9230 8052
Fax 80619 0
Email 80619 0
Contact person for scientific queries
Name 80620 0
Dr Brooke Devlin
Address 80620 0
Mary MacKillop Institute for Health Research
215 Spring St
Country 80620 0
Phone 80620 0
+61 3 9230 8052
Fax 80620 0
Email 80620 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
For ethical reasons, individual data will not be publicly available.
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary