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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
MATADOR: Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound
Scientific title
Effect of Intermittent Versus Continuous Energy Restriction on Body Weight, Resting Metabolic Rate and Neuroendocrine Function in Obese Men.
Secondary ID [1] 263026 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 270752 0
Condition category
Condition code
Metabolic and Endocrine 270932 270932 0 0
Normal metabolism and endocrine development and function
Diet and Nutrition 270942 270942 0 0

Study type
Description of intervention(s) / exposure
The study will comprise 3 phases: [1] Baseline energy balance, [2] Energy restriction intervention, and [3] Post-intervention energy balance. As we have previously shown that provision of food maximises dietary compliance in the free-living situation (1,2,4), food will be home-delivered weekly to participants in all phases of this study. The aim of PHASE 1 is to determine the baseline values of various parameters of the famine reaction before energy restriction and weight loss. During the 4 weeks of PHASE 1, weight stability will be achieved as we have previously published (1-4), by determining maintenance energy requirements from dietary history and resting metabolic rate (RMR), and then providing participants with a weight maintenance diet. In PHASE 2, participants will be randomised to continuous or intermittent energy restriction interventions. The continuous intervention consists of 16 weeks on a diet at 67% of maintenance energy requirements. The intermittent intervention consists of 16 weeks of total energy restriction administered as 2 weeks of energy restriction on a diet at 67% of maintenance energy requirements followed by 2 weeks of energy balance on a diet at 100% of maintenance energy requirements, for a total of 30 weeks. The interventions are designed to elicit a 10% body weight loss. To account for weight lost, the energy restriction will be indexed to body weight and RMR after every 4 weeks of energy restriction, thereby keeping theoretical relative energy deficit consistent across the 16-week period. In PHASE 3, participants will be placed on an energy balance diet referenced to their reduced-weight state for 4 weeks to examine the time course of recovery of metabolic and neuroendocrine markers. The macronutrient distribution in both energy restriction and energy balance diets will be maintained within the range of 25–30% of energy as fat, 15-20% as protein, and 50–60% as carbohydrate. As we have previously shown that provision of food maximises dietary compliance in the free-living situation (1,2,4), food will be home-delivered weekly to participants in this study.

1. Weinsier RL, Hunter GR, Desmond RA, Byrne NM, Zuckerman PA, Darnell BE. Free-living activity energy expenditure in women successful and unsuccessful at maintaining a normal body weight. Am J Clin Nutr. 2002; 75(3):499-504.
2. Byrne NM, Hills AP, Wood RE. Does body composition, relative energy deficit or adaptive thermogenesis explain differences between predicted and actual weight loss in obese adults? Obesity Reviews. 2010;11(Suppl.1):35-36.
3. Byrne NM, Weinsier RL, Hunter GR, et al. Influence of distribution of lean body mass on resting metabolic rate after weight loss and weight regain: comparison of responses in white and black women. Am J Clin Nutr. 2003;77(6):1368-73.
4. Wood RE, Byrne NM, Groves AM, Hills AP, King NK. Achieving energy balance in apparently sedentary obese males. Obesity Reviews. 2010;11(Suppl.1):219.
Intervention code [1] 269368 0
Treatment: Other
Intervention code [2] 269376 0
Comparator / control treatment
Continuous Energy Restriction is the control treatment
Control group

Primary outcome [1] 279596 0
Body weight will be measured using digital weighing scales. Digital weighing scales are to be used to monitor body weight of participants at home in times between laboratory visits. These scales will be calibrated regularly, and weight will also be measured at the standard laboratory sessions.
Timepoint [1] 279596 0
Daily - 4 weeks energy balance (pre-intervention)
Daily - 16 weeks (continuous) or 30 weeks (intermittent) energy restriction
Daily - 4 weeks energy balance (post-intervention)
Primary outcome [2] 279599 0
Resting metabolic rate via indirect calorimetry
Timepoint [2] 279599 0
Week 1 and 4 - energy balance (pre-intervention)
Week 4, 8, 12 and 16 - energy restriction
Week 2, 4 - energy balance (post-intervention)
Primary outcome [3] 279600 0
Neuroendocrine status: Overnight fasted blood samples will be collected and concentrations of the following analytes in serum or plasma will be determined: free T3, Free T4, reverse T3, TSH, ACTH, cortisol, testosterone, sex hormone binding globulin, IGF-1, and leptin.
Timepoint [3] 279600 0
Week 1 and 4 - energy balance (pre-intervention)
Week 4, 8, 12 and 16 - energy restriction
Week 1, 2, 4 - energy balance (post-intervention)
Secondary outcome [1] 294010 0
Body composition (Fat Mass and Fat-free Mass) will be assessed using the gold-standard 4-compartment model using air displacement plethysmography (via BodPod), deuterium dilution and Dual Energy X-ray Absorptiometry (DXA) at 4 time points: in energy balance immediately prior to (Phase 1), midway and immediately after the weight loss intervention (Phase 2) and after the 4-wk period of energy balance (Phase 3). In addition, BodPod measurements will be taken at week 1 energy balance (pre-intervention), weeks 4 and 12 of energy restriction, and weeks 1 and 2 of energy balance (post-intervention).
Timepoint [1] 294010 0
Week 1 and 4 - energy balance (pre-intervention)
Week 4, 8, 12 and 16 - energy restriction
Week 1, 2, 4 - energy balance (post-intervention)
Secondary outcome [2] 294011 0
Fasting substrate oxidation via indriect calorimetry
Timepoint [2] 294011 0
Week 1 and 4 - energy balance (pre-intervention)
Week 4, 8, 12 and 16 - energy restriction
Week 2, 4 - energy balance (post-intervention)
Secondary outcome [3] 294012 0
Markers of metabolic health (fasting serum glucose, insulin, triglycerides, cholesterol)
Timepoint [3] 294012 0
Week 1 and 4 - energy balance (pre-intervention)
Week 4, 8, 12 and 16 - energy restriction
Week 1, 2, 4 - energy balance (post-intervention)

Key inclusion criteria
Sedentary (< 60 mins physical activity per week)
Class I or II obese (30-40kg.m-2)
Waist circumference >102 cm
Euthyroid, non-diabetic, ambulatory, and weight stable for at least 6 months (+/-2kg)
Minimum age
25 Years
Maximum age
53 Years
Can healthy volunteers participate?
Key exclusion criteria
Diabetic or fasting blood glucose > 6.0 mmol/L (from medical screening)
Major surgery that will affect gut function/metabolic rate
Arthritis/musculoskeletal problems that would preclude full participation in all testing/affect activities of daily living
Heart condition
Sleep apnoea
Thyroid condition
Current smoker or gave up smoking within the last 6 months
Any medications known to affect metabolic rate or neuroendocrine function
Currently on a “diet” or actively losing weight

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Participants will be stratified according to BMI (30-34.9, 35-40) and age (25-38.9, 39-53) and then randomly allocated into either the intermittent energy restriction or continuous energy restriction groups.
Allocation is not concealed.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Pemuted block randomisation. Where intermittent energy restriction = 1 and continuous energy restriction = 2.
Where BMI (30-34.9) = A, BMI (35-40) = B, Age (25-38.9) = C, Age (39-53) = D. Each participant will therefore fall into one of four cell options: AC, AD, BC or BD. Each cell will have pair allocations of random sequence 1 or 2.
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

Recruitment status
Active, not recruiting
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] 269828 0
Government body
Name [1] 269828 0
National Health and Medical Research Council
Address [1] 269828 0
Level 1
16 Marcus Clarke Street
Canberra ACT 2601
Country [1] 269828 0
Primary sponsor type
Professor Nuala Byrne
Institute of Health and Biomedical Innovation
Queensland University of Technology
60 Musk Avenue
Kelvin Grove QLD 4059
Secondary sponsor category [1] 268860 0
Name [1] 268860 0
Queensland University of Technology
Address [1] 268860 0
2 George Street
Brisbane, QLD 4000
Country [1] 268860 0

Ethics approval
Ethics application status
Ethics committee name [1] 271796 0
University Human Research Ethics Committee (UHREC)
Ethics committee address [1] 271796 0
Governance and Legal Services
Queensland University of Technology
GPO Box 2434
2 George Street
Brisbane Q 4001
Ethics committee country [1] 271796 0
Date submitted for ethics approval [1] 271796 0
Approval date [1] 271796 0
Ethics approval number [1] 271796 0

Brief summary
There are more than 7 million overweight or obese adults in Australia and on average only about 5% of this population
achieve permanent weight reduction of any significance to their health. Many questions remain regarding the best way to achieve long-term weight loss, and how a person’s metabolic rate is affected both in the short- and long-term during dieting.
The overall aim of this project is to design more effective and sustainable weight loss strategies for overweight and obese adults. This study, funded by the National Health and Medical Research Council (NHMRC), aims to compare changes in weight and health using two different dieting approaches; one in which the energy intake (kilojoule value) changes every two weeks, and the other where the energy intake changes every four weeks. Throughout the intensive phase of the study, participants are provided with a healthy, balanced, energy-regulated diet delivered to their home. Measures of body composition, metabolic rate and energy expenditure, hunger and satiety, blood hormone levels, body fuel usage, and metabolic health will be taken at a number of time points throughout the study.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 33143 0
Address 33143 0
Country 33143 0
Phone 33143 0
Fax 33143 0
Email 33143 0
Contact person for public queries
Name 16390 0
Professor Nuala Byrne
Address 16390 0
Institute of Health and Biomedical Innovation
Queensland University of Technology
60 Musk Avenue
Kelvin Grove, QLD4059
Country 16390 0
Phone 16390 0
61 7 3138 6088
Fax 16390 0
61 7 3138 3606
Email 16390 0
Contact person for scientific queries
Name 7318 0
Professor Nuala Byrne
Address 7318 0
Institute of Health and Biomedical Innovation
Queensland University of Technology
60 Musk Avenue
Kelvin Grove, QLD4059
Country 7318 0
Phone 7318 0
61 7 3138 6088
Fax 7318 0
61 7 3138 3606
Email 7318 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