Trial Review

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been endorsed by the ANZCTR. Before participating in a study, talk to your health care provider and refer to this information for consumers
Trial registered on ANZCTR


Registration number
ACTRN12617000129381
Ethics application status
Approved
Date submitted
17/01/2017
Date registered
24/01/2017
Date last updated
24/01/2017
Type of registration
Retrospectively registered

Titles & IDs
Public title
Food product health warnings promote healthy dietary decision making.
Scientific title
Health warnings promote healthier dietary decision making in healthy participants: effects of message framing and graphic versus text-based warnings.
Secondary ID [1] 290949 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 301683 0
Dietary decision making 301684 0
Condition category
Condition code
Public Health 301392 301392 0 0
Health promotion/education
Diet and Nutrition 301450 301450 0 0
Obesity

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
The intervention entails presentation with obesity-prevention health warnings designed to be used in health promotion campaigns at point-of-sale or on food product packaging. Ten health warning messages (derived from the NHMRC Dietary Guidelines for Australians, 2013) were used to create 40 health warnings across four health warning design groups (text-based or text-and-graphic health warnings presented with positive or negative message framing), by altering the message framing and image content of the warnings. An example of a negatively framed health warning message is “Being overweight increases your risk of heart disease.” The positively framed variant of this message reads, “Maintaining a healthy weight reduces your risk of heart disease.” Similarly, the negative graphic variant of this message features an image of an unhealthy heart affected by heart disease, while the positive graphic variant features a stylised ‘healthy’ heart arranged out of fruit and vegetable products. The intervention is delivered at the midpoint (see below) of a single testing session conducted at The University of Melbourne's decision neuroscience laboratory.

All participants complete an unprimed/baseline test phase in which they make dietary choices prior to exposure to health warnings. Following this phase, all participants are instructed to attend to and read 10 health warning messages/images (each participants is presented with 10 health warnings of a single health warning format, e.g. participants in the positively framed, text warning group see only positively framed, text-based warnings; text based health warnings were 500 x 300 pixels; graphic health warnings were 500 x 500 pixels) presented centrally on a computer monitor for 8 seconds each (with a 2 - 6 second break between each presentation). During the intervention presentation phase of the experiment, participants are instructed to press the space bar if the border around the health warning stimulus changes colour (which occurs on a random 3 trials out of the total 10), to ensure that participants attend to the health warning messages. Following delivery of the intervention, participants complete a primed/test phase of the same dietary choice task. Participants are allowed to take a self-paced break between the baseline phase, the intervention delivery, and then the test phase. The baseline and test phases are approximately 40 minutes long, while the intervention presentation phase lasts approximately 8 minutes.
Intervention code [1] 296897 0
Prevention
Intervention code [2] 296898 0
Lifestyle
Intervention code [3] 296899 0
Behaviour
Comparator / control treatment
This study features a within participant control (in the form of a pre-intervention baseline period) and a between groups control (in the form of a control group who are presented with a message free image that is visually analogous to the health warning stimuli used in the test conditions.

Control health warning images were created by replacing the words in the health warning message with non-words of equivalent length from the ARC non-word database. The images used in the graphic variants of the health warning images were masked by randomly sorting the pixels of the image horizontally and then applying a high frequency noise filter. At the completion of the experiment, participants are given an open ended questionnaire to ensure that participants in the control group did not guess the purpose of the study.
Control group
Active

Outcomes
Primary outcome [1] 300789 0
Dietary self-control measure assessing participants’ frequency of choosing healthy but not tasty items and rejecting unhealthy yet tasty items in a dietary decision task.
This measure was adapted from the dietary self-control measure used by Harris, Hare & Rangel (2013), but was altered to work for our task by allowing participants to respond on a continuous, rather than binary, scale (i.e. participants can indicate whether they want to eat a particular food item, and also indicate how much they do or do not want to eat this item).

Reference.
Harris A., Hare T., Rangel A. (2013). Temporally dissociable mechanisms of self-control: Early attentional filtering versus late value modulation. The Journal of Neuroscience, 33, 18917–18931.
Timepoint [1] 300789 0
Following exposure to food product health warnings.
Secondary outcome [1] 330865 0
None
Timepoint [1] 330865 0
None

Eligibility
Key inclusion criteria
- Men and women aged 18-70 years.
- Right-handed.
- Familiar with common Australian supermarket snack food brands.
- Fluent in spoken and written English.
Minimum age
18 Years
Maximum age
70 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Subjects will be excluded if they:
- Are currently restricting their diet.
- Have any medical, ethical, religious or other belief or condition (e.g. coeliac disease, diabetes or following a vegan diet) limiting the consumption of common snack food brands.
- Have a past or current eating disorder diagnosis.
- Have any food allergies.
- Are pregnant.

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)
Participants are unaware of the purpose of the study. At commencement of the experimental task, MATLAB’s random number generation functions are used to allocate participants a condition code from 1-5, which determines the type of health warnings that that participant will see. This method of group allocation is concealed by its nature.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Random trial sequence generation using MATLAB's random number generation functions.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Other
Other design features
The study featured a crossed factorial experimental design, in which participants completed an pre-intervention experimental stage, and were then randomly allocated into test groups (text-based, positively framed health warnings; text-based, negatively framed health warnings; text-and-graphic, positively framed health warnings; text-and-graphic, negatively framed health warnings; control group). Each participant then completed a second, post-intervention stage. An interaction effect between the between groups and repeated measures factors was taken as evidence that health warnings influence dietary decision making.
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
Linear mixed effects modelling using backwards selection. Participants and food items specified as random effects. Satterthwaite degrees of freedom approximation is used to calculate p-values.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
1/02/2016
Date of last participant enrolment
Anticipated
Actual
31/05/2016
Date of last data collection
Anticipated
Actual
16/06/2016
Sample size
Target
96
Accrual to date
Final
96
Recruitment in Australia
Recruitment state(s)
VIC

Funding & Sponsors
Funding source category [1] 295372 0
Charities/Societies/Foundations
Name [1] 295372 0
The Cancer Council Victoria
Country [1] 295372 0
Australia
Primary sponsor type
Individual
Name
Daniel Rosenblatt
Address
The University of Melbourne
Melbourne School of Psychological Sciences
Redmond Barry Building, Building 115
Tin Alley, Parkville VIC 3010
Country
Australia
Secondary sponsor category [1] 294217 0
Individual
Name [1] 294217 0
Melanie Wakefield
Address [1] 294217 0
Cancer Council Victoria,
Centre for Behavioural Research in Cancer,
615 St Kilda Road,
Melbourne VIC 3004
Country [1] 294217 0
Australia
Secondary sponsor category [2] 294218 0
Individual
Name [2] 294218 0
Stefan Bode
Address [2] 294218 0
The University of Melbourne
Melbourne School of Psychological Sciences
Redmond Barry Building, Building 115
Tin Alley, Parkville VIC 3010
Country [2] 294218 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 296706 0
University of Melbourne Human Research Ethics Committee
Ethics committee address [1] 296706 0
The University of Melbourne, Parkville VIC 3010
Ethics committee country [1] 296706 0
Australia
Date submitted for ethics approval [1] 296706 0
18/12/2014
Approval date [1] 296706 0
26/01/2015
Ethics approval number [1] 296706 0
1443258

Summary
Brief summary
Following successful use in tobacco control, health warnings on food products and at point-of-sale have been proposed as a potential obesity prevention measure. This study aims to investigate the efficacy of food product health warnings for promoting healthy dietary decision making. Additionally, the study aims to investigate the degree to which two key health warning design factors (text-based health warnings versus text-and-graphic health warnings; health warnings featuring positively versus negatively framed messages) influence health warning efficacy.

Ninety-six participants will be recruited to complete a mixed design dietary self-control experiment conducted as a single session. The experiment features four stages; the rating stage, the unprimed decision stage, the priming stage, and the primed decision stage. In the first stage, participants will be shown a selection of 100 common Australian snack foods (including chocolate, chips, cookies, fruit, nuts and vegetables) and asked to provide subjective health and taste ratings for each food item. In the unprimed (baseline) decision stage, participants will be shown half of the food items they rated in the first stage and asked to indicate which of these items they would like to eat at the end of the experiment. Prior to the priming stage, participants will be randomly allocated to one of five health warning format conditions; text-based, negative framing (n = 16); graphic, negative framing (n = 16); text, positive framing (n = 16); graphic, positive framing (n = 16); control group (n = 32). During the priming stage, participants will be exposed to health warnings of their allocated format only. In the primed decision stage participants will be shown the remaining half of the snack food items and again asked to indicate which foods they would like to consume at the end of the experiment.

A measure of dietary self-control will be calculated based on the proportion of healthy but not tasty items chosen for consumption and the number of unhealthy yet tasty items rejected. Participants will be granted one of their chosen items to eat and will be asked to complete demographic and dietary behaviour questionnaires at the end of the experiment.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 71826 0
Mr Daniel Rosenblatt
Address 71826 0
Melbourne School of Psychological Sciences
Redmond Barry Building,
The University of Melbourne,
Parkville VIC 3010
Country 71826 0
Australia
Phone 71826 0
+61383444446
Fax 71826 0
Email 71826 0
[email protected]
Contact person for public queries
Name 71827 0
Mr Daniel Rosenblatt
Address 71827 0
Melbourne School of Psychological Sciences
Redmond Barry Building,
The University of Melbourne,
Parkville VIC 3010
Country 71827 0
Australia
Phone 71827 0
+61383444446
Fax 71827 0
Email 71827 0
[email protected]
Contact person for scientific queries
Name 71828 0
Mr Daniel Rosenblatt
Address 71828 0
Melbourne School of Psychological Sciences
Redmond Barry Building,
The University of Melbourne,
Parkville VIC 3010
Country 71828 0
Australia
Phone 71828 0
+61383444446
Fax 71828 0
Email 71828 0
[email protected]

No information has been provided regarding IPD availability


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.