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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Retrospectively registered

Titles & IDs
Public title
Effects of oral protein load on the rate of gastric emptying, intragastric meal distribution, gastrointestinal hormone release, appetite sensations and energy intake in lean subjects.
Scientific title
Effects of oral protein load on the rate of gastric emptying, intragastric meal distribution, gastrointestinal hormone release, appetite sensations and energy intake in lean subjects.
Secondary ID [1] 262197 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 265879 0
Gastric emptying 268279 0
Intragastric meal distribution 268280 0
Gastrointestinal hormone release 268281 0
Appetite sensations 268282 0
Condition category
Condition code
Diet and Nutrition 266037 266037 0 0
Metabolic and Endocrine 268415 268415 0 0
Normal metabolism and endocrine development and function

Study type
Description of intervention(s) / exposure
The participant will receive a single 450mL preload per study visit (separated by at least 3 days) in a randomised, crossover fashion of: i) 30 grams Whey Protein Isolate with diet lime cordial flavouring ii) 70 grams Whey Protein Isolate with diet lime cordial flavouring or iii) Water control with diet lime cordial flavouring. All preloads contain measured amounts of saline solution to match the osmolarity of each drink, and 100uL of 13C Octanoic acid to enable measurement of gastric emptying via 13CO2 in the breath. Gastric emptying rate and intragastric meal distribution using 3D ultrasound, hormone concentrations by blood sampling, appetite sensation questionnaires in the form of a Visual Analogue Scale (VAS), and subsequent energy intake will be measured. A buffet meal will be provided at 180 mins following the preload and the participant will have 30 minutes to eat until comfortably full. The buffet meal consists of 300mL orange juice, 600mL water, 375mL iced coffee, 4 slices white bread, 4 slices brown bread, 100g deli leg ham, 100g virginian chicken, 4 slices cheese, 100g tomato, 100g cucumber, 100g lettuce, 2 portions mayonnaise, 2 portions margarine, 1 medium red delicious apple, 1 medium banana, 200g chocolate custard, 150g fruit salad, 200g strawberry yoghurt, and a 14g milky way chocolate bar. Each volunteer will receive one of each of the 3 treatments on each of the 3 study days. Each study visit will be separated by no less than 3 days. Each visit will last approximately 4 hours.
Intervention code [1] 266872 0
Other interventions
Comparator / control treatment
Placebo: a single 450mL water and diet lime cordial preload
Control group

Primary outcome [1] 269093 0
Macronutrient and total energy intake at the buffet meal will be analysed using the FoodWorks software program.
Timepoint [1] 269093 0
Buffet meal will be presented at 180 minutes following the last ultrasound measurement and the subject will be allowed to freely consume food until comfortably full for 30 minutes (until t= 210 minutes)
Primary outcome [2] 269097 0
Gut hormone release: cholecyctokinin (CCK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), neuropeptide W (NPW), and ghrelin. Plasma glucose and serum insulin. Gut hormones will be assessed by Enzyme-Linked Immunosorbent Assay (ELISA)/Radioimmunoassay (RIA) from the blood samples taken.
Timepoint [2] 269097 0
Blood samples will be taken at time points: -15 minutes, 0 minutes (baseline) and every fifteen minutes thereafter until 180 minutes. The final blood sample will be taken at 210 minutes, after the buffet meal has been consumed.
Primary outcome [3] 269098 0
Gastric emptying rate assessed by three-dimensional (3D) ultrasonography and 13C Octanoic Acid Breath Test.

3D ultrasound will define the fraction of the meal emptied from the stomach during the study. The 50% emptying time (T1/2) will also be obtained.

The 13C Octanoic Acid breath test will assess gastric emptying of the protein drink through measurement of 13CO2 in the breath via mass spectrometry. Half-emptying time and gastric emptying coefficient will also be calculated and compared to those obtained using 3D ultrasonography.
Timepoint [3] 269098 0
Ultrasound measurements for assessment of gastric emptying will be taken at -15, 0, and every 15 minutes thereafter until 180 minutes.

Breath samples will be collected for assessment of 13CO2 immediately before meal ingestion, and every 5 minutes for the 30 minutes following meal ingestion. Breath samples will then be collected every 15 minutes until 180 minutes.
Secondary outcome [1] 276923 0
Appetite sensations using a Visual Analogue Scale (VAS) (nausea, bloating, hunger, fullness, desire to eat, and amount of food desired to eat)
Timepoint [1] 276923 0
VAS is administered at time points: -15 minutes, 0 minutes (baseline) and every fifteen minutes thereafter until 180 minutes. The final VAS is administered at 210 minutes after the buffet meal has been consumed.

Key inclusion criteria
non-obese with a body mass index of 19-25kg/m2 and weight stable (<5% fluctuation in body weight in previous 3 months)
Minimum age
18 Years
Maximum age
55 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
1) Significant gastrointestinal symptoms; disease or surgery 2) Use of prescribed or non-prescribed medications (including vitamins and herbal supplements) which may effect energy metabolism, GI function, body weight or appetite (eg domperidone and cisapride, anticholinergic drugs (eg. atropine), metoclopramide, erythromycin, hyoscine, orlistate, green tea extracts, astragalus, St. johns Wort etc.) 3) Diabetes mellitus, epilepsy, cardiovascular or respiratory disease, or any other significant illness as assessed by the investigator 4) Intake of >20g alcohol on a daily basis 5) Smokers (cigarettes, cigars, marijuana) 6) In female subjects, pregnancy or lactation. A pregancy test will be performed in all female subjects of childbearing potential, using a urine sample, prior to commencement of the study and subsequently prior to each study day 7) Restrained eaters, as determined by a score of >12 on the eating restraint questionnaire component of the 3 factor eating questionnaire 8) Donation of blood in the past 12 weeks prior to enrolment in the study. Subjects will also be advised to abstain from donating blood for 12 weeks following study completion 9) Consumption of a vegetarian diet.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Volunteers are asked to visit the clinic for a 30-45 minute screening visit. A signed consent form is obtained then a questionnaire is answered by the volunteer based on the inclusion/exclusion criteria and a blood sample is collected for haemoglobin and iron levels. Eligibility is determined. Eligible volunteers are assigned a subject number and randomised into treatment for each study visit, using a randomisation table which was created on an excel spreadsheet. Randomisation involved contacting the holder (study assistant) of the randomisation table to inform them of the next subject's details and study dates. The unblinded study assistant is therefore responsible for allocating a random treatment to the subject and preparing the solution on each study day.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The randomisation table was generated using Microsoft Office Excel.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

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] 4167 0
Recruitment postcode(s) [2] 4168 0
Recruitment postcode(s) [3] 4169 0
Recruitment postcode(s) [4] 4170 0
Recruitment postcode(s) [5] 4171 0
Recruitment postcode(s) [6] 4172 0
Recruitment postcode(s) [7] 4173 0
Recruitment postcode(s) [8] 4174 0
Recruitment postcode(s) [9] 4175 0

Funding & Sponsors
Funding source category [1] 267350 0
Government body
Name [1] 267350 0
National Health and Medical research Council Grant
Address [1] 267350 0
Level 1, 16 Marcus Clark Street, Canberra ACT 2601
Country [1] 267350 0
Primary sponsor type
Dr Natalie Luscombe-Marsh
Level 6, Eleanor Harrald Building, Frome Road, Adelaide, SA 5000
Secondary sponsor category [1] 266416 0
Name [1] 266416 0
University of Adelaide
Address [1] 266416 0
North Terrace,
Adelaide, SA 5005
Country [1] 266416 0

Ethics approval
Ethics application status
Ethics committee name [1] 269328 0
Royal Adelaide Hospital Research Ethics Committee
Ethics committee address [1] 269328 0
Level 3, Hanson Institute, North Terrace, Adelaide, SA 5000
Ethics committee country [1] 269328 0
Date submitted for ethics approval [1] 269328 0
Approval date [1] 269328 0
Ethics approval number [1] 269328 0

Brief summary
The ingestion of nutrients induces a number of changes in gastrointestinal function which are associated with the modulation of appetite and energy intake. These changes include the slowing of gastric emptying, which sustains gastric distension and is associated with proximal gastric relaxation and changes in small intestinal motility. It has been established that fat and carbohydrate empty from the stomach at an overall rate of 1-3kcal/minute irrespective of volume, while the load of fat and carbohydrate is known to effect gastrointestinal motor activity and slow gastric emptying rate. To date, research documenting the gastric emptying rate of protein is limited and the effect of varying the protein load has not been characterised. Moreover, the relationship between gastric emptying and the regulation of energy intake by dietary protein remains unclear.

Effects on gastrointestinal hormone release also occur with macronutrient ingestion. Small intestinal administration of fat has been shown to increase plasma CCK, PYY, and GLP-1 to a greater extent than carbohydrate in both healthy young and older men. However, evidence for load-dependent effects of protein on gut hormones is inconsistent. Since these gastrointestinal hormones have an important role in the regulation of appetite and energy intake, it is imperative that changes in the magnitude and temporal pattern of their release is established in response to varying protein loads and also related to changes in gastric emptying and intragastric meal distribution.

Thus, this study has been designed to investigate how the load of orally administered Whey Protein Isolate effects gastric emptying rate, intragastric meal distribution, gut hormone concentrations, appetite sensations, and subsequent energy intake in healthy, lean individuals.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 32622 0
Dr Dr Natalie Luscombe-Marsh
Address 32622 0
Level 6, Eleanor Harrald Building, Frome Road, Adelaide, SA 5000
Country 32622 0
Phone 32622 0
+61 08 8222 5038
Fax 32622 0
+61 8 8223 3870
Email 32622 0
Contact person for public queries
Name 15869 0
Dr Dr Natalie Luscombe-Marsh
Address 15869 0
Level 6, Eleanor Harrald Building, Frome Road, Adelaide, SA 5000
Country 15869 0
Phone 15869 0
+61 08 8222 5038
Fax 15869 0
Email 15869 0
Contact person for scientific queries
Name 6797 0
Dr Dr Natalie Luscombe-Marsh
Address 6797 0
Level 6, Eleanor Harrald Building, Frome Road, Adelaide, SA 5000
Country 6797 0
Phone 6797 0
+61 08 8222 5038
Fax 6797 0
Email 6797 0

No information has been provided regarding IPD availability
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