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Trial registered on ANZCTR

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

Titles & IDs
Public title
Identifying why some people consume excess fat. A twin study.
Scientific title
In healthy twin pairs, does a high fat diet over an eight week period, compared with a low fat diet, result in decreased sensitivity to the taste of fatty acids, lower satiety levels and increased preferences for high fat foods.
Secondary ID [1] 282390 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 288971 0
Condition category
Condition code
Diet and Nutrition 289309 289309 0 0

Study type
Description of intervention(s) / exposure
Eight week dietary intervention that is either high- or low-fat. These diets are equated for energy intake, with the high-fat diet consisting of 40% fat, 25% protein and 35% carbohydrate. The low-fat diet will consist of 20% fat, 25% protein and 55% carbohydrate. Diets will consist of different caloric intake for each individual participant based on their energy needs. Participants will have an initial consultation with a dietician (approx. 30 mins) prior to commencing the diet, and will be provided supplemental foods every two weeks throughout the intervention to assist with adherence to the diet. Further, participants will complete a one-day diet diary each week, and receive one short (5-10min) phone call each week to monitor compliance.
Intervention code [1] 287022 0
Intervention code [2] 287023 0
Treatment: Other
Intervention code [3] 287028 0
Comparator / control treatment
The high-fat diet will be compared with a low-fat diet consumed for the same period of time.
Control group

Primary outcome [1] 289423 0
Taste sensitivity to fatty acids, as measured by determining the participant's threshold for detecting fatty acids in a milk solution. Participants will be given two control milk samples, with no fatty acid, and a third sample with increasing fatty acid concentration. Taste threshold will be determined when participants can correctly identify the milk with fatty acid identified three times in a row.
Timepoint [1] 289423 0
Assessed at baseline, week four and week eight of the dietary intervention.
Primary outcome [2] 289424 0
Preference for high fat foods. Participants will be given a series of high and low fat options (e.g. full fat compared with fat free chocolate mousse), without knowing which is which, and will have to choose which they prefer.
Timepoint [2] 289424 0
Assessed at baseline, week four and week eight of the dietary intervention.
Primary outcome [3] 289425 0
Fatty acid taste receptor expression. This will be determined by biopsy of fungiform papillae and subsequent RNA expression analysis.
Timepoint [3] 289425 0
Assessed at baseline and week eight of the dietary intervention.
Secondary outcome [1] 302446 0
PROP sensitivity. Participants will be given a sample of PROP, and will have to rate how it tastes on a general labelled magnitude scale.
Timepoint [1] 302446 0
Secondary outcome [2] 302447 0
Papillae density. This is measured by staining the tongue with blue food dye in order to see the papillae more clearly. The tongue will be photographed, and the papillae within a certain area will be counted.
Timepoint [2] 302447 0
Secondary outcome [3] 302448 0
Fat ranking ability. This will be tested by giving participants four custard samples with different fat concentrations, and asking them to rank them from highest to lowest fat.
Timepoint [3] 302448 0
Baseline, week four and week eight of the dietary intervention.
Secondary outcome [4] 302449 0
Lingual lipase, as determined by saliva samples.
Timepoint [4] 302449 0
Baseline, week four and week eight of the dietary intervention.

Key inclusion criteria
Must be a twin (monozygotic or dizygotic). Must be able to speak English (as information and consent forms will not be translated).
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Individuals under 18. Individuals who do not speak English. Individuals who are not twins.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
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)

Funding & Sponsors
Funding source category [1] 287167 0
Government body
Name [1] 287167 0
National Health and Medical Research Council
Address [1] 287167 0
Level 1
16 Marcus Clarke Street
Canberra ACT 2601
Country [1] 287167 0
Primary sponsor type
Deakin University
221 Burwood Hwy,
Burwood, 3125
Secondary sponsor category [1] 285933 0
Government body
Name [1] 285933 0
Address [1] 285933 0
CSIRO Enquiries
Locked Bag 10
Clayton South VIC 3169

Country [1] 285933 0

Ethics approval
Ethics application status
Ethics committee name [1] 289163 0
Deakin Human Research Ethics Committee
Ethics committee address [1] 289163 0
221 Burwood Hwy,
Burwood, 3125
Ethics committee country [1] 289163 0
Date submitted for ethics approval [1] 289163 0
Approval date [1] 289163 0
Ethics approval number [1] 289163 0

Brief summary
Obesity is a major health issue that is currently affecting millions of Australians, in addition to having a high economic cost both in this country and around the world. Some individuals are more susceptible to obesity than others; one factor may be variance in the taste system due to genetic and environmental factors such as diet. The present study aims to identify and investigate the mechanisms linking individual differences in taste with obesity. The mechanisms thought to be in play relate to our sense of taste, including taste receptors and their responsiveness to fatty acids, satiety levels resulting from consuming high fat foods, and food preferences. It is predicted that for susceptible individuals, consuming a high fat diet will negatively influence their responsiveness to fatty acids, increase their preference for high fat foods and decrease their hormonal and perceived satiety levels following food consumption. Each of these mechanisms has the potential to lead to an increase in dietary fat consumption, and BMI. Previous research has indicated that within pairs of BMI discordant monozygotic twins, the twin with the higher BMI has significantly lower taste responses to fatty acids, indicating that their diet may be related to their fatty acid taste sensitivity.
This study aims to include 100 twin pairs (half monozygotic and half dizygotic) recruited from the Australian Twin Registry. These participants will be over 18 years of age. Twin pairs will be randomized into one of two weight maintenance diets (high- or low-fat). Participants will consume this allocated diet for eight weeks, with weekly diet diaries being assessed for compliance, in addition to weekly satiety questionnaires. Prior to baseline testing, participants will complete a four-day diet diary, the Cancer Council of Victoria food frequency questionnaire, the restrained eaters questionnaire, and a like-dislike questionnaire. Further testing will occur at baseline, week four and week eight. Each testing session will include a 24-hour dietary recall, taste function assessment, a fat-ranking task using custards, saliva samples, papillae density testing, preference testing for seven regular and low fat foods, anthropometry and a fungiform papillae biopsy. During baseline testing, participants will also be tested for PROP sensitivity, which is a heritable trait. Results will be compared at each time point to determine the effect of a high- or low-fat diet on fatty acid taste responses and satiety.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 39526 0
Prof Russell Keast
Address 39526 0
School of Exercise and Nutrition Sciences
Deakin University
221 Burwood Hwy,
Burwood, 3125
Country 39526 0
Phone 39526 0
+61 3 924 46944
Fax 39526 0
Email 39526 0
Contact person for public queries
Name 39527 0
Prof Russell Keast
Address 39527 0
School of Exercise and Nutrition Sciences
Deakin University
221 Burwood Hwy,
Burwood, 3125
Country 39527 0
Phone 39527 0
+61 3 924 46944
Fax 39527 0
Email 39527 0
Contact person for scientific queries
Name 39528 0
Prof Russell Keast
Address 39528 0
School of Exercise and Nutrition Sciences
Deakin University
221 Burwood Hwy,
Burwood, 3125
Country 39528 0
Phone 39528 0
+61 3 924 46944
Fax 39528 0
Email 39528 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