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Trial registered on ANZCTR


Registration number
ACTRN12616000599471
Ethics application status
Approved
Date submitted
6/05/2016
Date registered
10/05/2016
Date last updated
10/05/2016
Type of registration
Retrospectively registered

Titles & IDs
Public title
Effect of varying dietary protein concentration with carbohydrate versus fat on energy intake in healthy adults
Scientific title
Interactions between protein leverage and dietary carbohydrate and fat content in the control of energy intake in humans
Secondary ID [1] 289146 0
Nil Known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
obesity 298660 0
Condition category
Condition code
Diet and Nutrition 298721 298721 0 0
Obesity

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Each participant attended four, 4-day periods of in-house dietary manipulation. Participants will be given ad libitum access to diets containing varying protein content (10% and 25%), and the nutrient used to adjust dietary protein concentrations (carbohydrate or fat). The 4 diet treatments will be matched for palatability and energy density. The 4 diet composition will be as follows:

Fixed fat, variable carbohydrate
Diet 1: 10% protein, 30% fat and 60% carbohydrate
Diet 2: 25% protein, 30% fat, 45% carbohydrate

Fixed carbohydrate and variable fat
Diet 3: 10% protein, 40% fat and 50% carbohydrate
Diet 4: 25% protein, 25% fat and 50% carbohydrate

Participants will be given ad libitum access to study food with no access to other foods during each intervention period. Participants will have free access to a variety of foods all day and can initiate their own meal times. Participants will be asked to leave any uneaten foods and/or empty packages in a designated bag.

Food intake will be measured by recording the weight of food before and after serving, to the nearest gram. Energy intake will be calculated using the nutritional information for each recipe. The trial will be a randomised cross-over trial, each participant completed each of the four 4-day interventions with at least a one week washout period between interventions.
Intervention code [1] 294663 0
Lifestyle
Intervention code [2] 294678 0
Prevention
Comparator / control treatment
The trial was a randomised crossover trial, each participant was their own control. None of the four diets will act as the comparator/control.
Control group
Active

Outcomes
Primary outcome [1] 298198 0
Energy intake (MJ): Participants will be given ad libitum access to study food with no access to other foods during each intervention period. Participants will have free access to a variety of foods all day and could initiate their own meal times. Participants will be asked to leave any uneaten foods and/or empty packages in a designated bag. Food intake will be measured by recording the weight of the food before and after serving to the nearest gram. Total energy intake will then be calculated using the nutritional information for each recipe.
Timepoint [1] 298198 0
Provided foods will be weighed at the beginning of each day and food intake will be monitored and weighed by the study coordinator every 1-2 hours from 7am until 7pm. Any leftover or empty packages from foods consumed overnight (7pm-7am) will be weighed at 7am the next day.
Secondary outcome [1] 323461 0
Fasted serum levels of glucose
Timepoint [1] 323461 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [2] 323462 0
Fasted serum levels of triglycerides
Timepoint [2] 323462 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [3] 323463 0
Fasted serum levels of total cholesterol
Timepoint [3] 323463 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [4] 323464 0
Fasted serum levels of HDL cholesterol
Timepoint [4] 323464 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [5] 323465 0
Fasted serum levels of urea
Timepoint [5] 323465 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [6] 323466 0
Fasted serum levels of protein
Timepoint [6] 323466 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [7] 323467 0
Fasted serum levels of albumin
Timepoint [7] 323467 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [8] 323468 0
Fasted plasma levels of fibroblast growth factor-21
Timepoint [8] 323468 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [9] 323469 0
24 hour levels of urinary urea
Timepoint [9] 323469 0
Measured the day prior to and on day 4 of the four interventions.
Secondary outcome [10] 323470 0
Glucose control measured by continuous Glucose Monitoring System
Timepoint [10] 323470 0
Measured throughout each of the four 4-day interventions.
Secondary outcome [11] 323471 0
Sleep duration measured by Actiwatch
Timepoint [11] 323471 0
Measured throughout each of the four 4-day interventions.
Secondary outcome [12] 323472 0
Levels of activity measured by Actiwatch
Timepoint [12] 323472 0
Measured throughout each of the four 4-day interventions.
Secondary outcome [13] 323473 0
Appetite rating using visual analogue scales
Timepoint [13] 323473 0
Appetite questionnaires were administered hourly from before breakfast until 22:00 on day 4
Secondary outcome [14] 323474 0
Food palatability ratings using visual analogue scales
Timepoint [14] 323474 0
Palatability questionnaires were administered for each food consumed on day 4
Secondary outcome [15] 323475 0
Blood pressure was measured by Omron Standard Blood Pressure Monitor
Timepoint [15] 323475 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [16] 323476 0
Body weight using a digital scale
Timepoint [16] 323476 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [17] 323477 0
Waist circumference using a tape measure
Timepoint [17] 323477 0
Measured on the morning of day 1 prior to and on the morning of day 5 following each of the four 4-day interventions.
Secondary outcome [18] 323478 0
Body height using a fixed stadiometer.
Timepoint [18] 323478 0
Measured on day 1 of the first of the four dietary interventions.

Eligibility
Key inclusion criteria
Lean (BMI < 25 kg/m2), healthy male and female participants
Minimum age
18 Years
Maximum age
65 Years
Gender
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Pregnancy or planning pregnancy, breastfeeding, known diabetes, known unstable or untreated elevated blood pressure or cholesterol, cardiovascular disease, chronic inflammatory conditions, medications that interfere with glucose metabolism, smoking, alcohol consumption above current NHMRC dietary guidelines, allergy or intolerance to any of the intervention foods, irregular eating patterns or eating disorder, following a weight reducing diet. Vegetarians and Vegans will be excluded to aid preparation of covertly manipulated foods.

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Each subject was screened to determine eligibility for the study. At this point the trial coordinator was unaware of the sequence of interventions the subject would be allocated. Once it was determined that the participant was eligible to be included in the trial the participant was then randomly allocated an order of intervention. Allocation of order was concealed by randomly selecting a sequence from an envelope.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
All possible sequences of interventions were printed the same number of times and placed in an envelope prior to the start of the study. The total number of sequences printed exceeded the number of participants that would be required to complete the trial. A sequence was randomly selected from the envelope for each participant.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Crossover
Other design features
Within subject design, each participant completed each of the interventions.
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
The study aims to recruit 30 lean subjects, comprising equal numbers of males and females. The sample size calculation was based on a previous ad libitum study where a 4.5MJ change in energy intake was measured in response to a reduction in percent dietary protein from 15% to 8% with a standard deviation of differences within pairs of approximately 1.2MJ. In order to detect a difference of 0.8MJ with a power of 80%, a significance of <0.05 using a within subjects design, a sample size of 20 will be required. Recruitment of 30 subjects would allow for a dropout of 30%.

Mixed model linear regression will be used to test for significant effects of the interventions and for differences in the change from baseline between each intervention for measurements taken prior to and following each intervention. Data will be presented as means and standard errors, an a p value of < 0.05 will be accepted as significant. Estimates from the mixed model linear regression will also be presented alongside confidence intervals.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
NSW
Recruitment hospital [1] 5744 0
Royal Prince Alfred Hospital - Camperdown
Recruitment postcode(s) [1] 13213 0
2050 - Camperdown

Funding & Sponsors
Funding source category [1] 293525 0
Government body
Name [1] 293525 0
National Health and Medical Research Council
Address [1] 293525 0
Level 1, 16 Marcus Clarke Street, Canberra, ACT 2601
Country [1] 293525 0
Australia
Primary sponsor type
University
Name
The University of Sydney
Address
The University of Sydney, NSW 2006
Country
Australia
Secondary sponsor category [1] 292345 0
Individual
Name [1] 292345 0
Alison Gosby
Address [1] 292345 0
The University of Sydney, NSW 2006
Country [1] 292345 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 294963 0
Sydney Local Health District
Ethics committee address [1] 294963 0
Research Development Office
Level 11, KGV Building
Missenden Road
Royal Prince Alfred Hospital
Camperdown, NSW 2050
Ethics committee country [1] 294963 0
Australia
Date submitted for ethics approval [1] 294963 0
11/05/2011
Approval date [1] 294963 0
02/06/2011
Ethics approval number [1] 294963 0
X11-0139 & HREC/11/RPAH/194

Summary
Brief summary
Protein intake has remained relatively stable through the development of the obesity epidemic. The protein leverage hypothesis proposes that a separate and dominant appetite for protein drives excess energy intake when dietary protein is diluted by fat and carbohydrate. We have provided convincing evidence that when the percent protein of the diet is reduced from 25% to 10% by increasing percent carbohydrate and keeping fat constant at 30% lean humans respond by increasing total energy intake. Recent data from a rodent dietary model suggests that intake of protein and carbohydrate is regulated (with protein dominating) but intake of fat is not. If dietary fat is not regulated in humans we would predict that the protein leverage effect will be even stronger if protein and fat co-vary in experimental diets and carbohydrate is kept constant at an adequate level. The aim of the study is to test whether converse changes in fat rather than carbohydrate will accentuate the protein leverage effect in covert trials. To do this we will manipulate the protein to energy ratio of the diet by increasing or decreasing the protein content whilst respectively decreasing or increasing the carbohydrate or fat content on 4 occasions for 4-days.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 65642 0
Prof Stephen Simpson
Address 65642 0
Charles Perkins Centre, Bldg D17, The University of Sydney, NSW 2006
Country 65642 0
Australia
Phone 65642 0
+61 2 8627 1613
Fax 65642 0
Email 65642 0
stephen.simpson@sydney.edu.au
Contact person for public queries
Name 65643 0
Dr Alison Gosby
Address 65643 0
Charles Perkins Centre, Bldg D17, The University of Sydney, NSW 2006
Country 65643 0
Australia
Phone 65643 0
+61 2 8627 1689
Fax 65643 0
Email 65643 0
alison.gosby@sydney.edu.au
Contact person for scientific queries
Name 65644 0
Dr Alison Gosby
Address 65644 0
Charles Perkins Centre, Bldg D17, The University of Sydney, NSW 2006
Country 65644 0
Australia
Phone 65644 0
+61 2 8627 1689
Fax 65644 0
Email 65644 0
alison.gosby@sydney.edu.au

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