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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
The thermoneutral zone- Can we use ambient temperature to aid health
Scientific title
Investigation into the effect of mild cold exposure and temperature variations on energy expenditure in healthy adults- Determining the Thermoneutral Zone.
Secondary ID [1] 290213 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Thermoregulation 300387 0
Metabolism 300388 0
Condition category
Condition code
Metabolic and Endocrine 300252 300252 0 0
Normal metabolism and endocrine development and function

Study type
Description of intervention(s) / exposure
The intervention in this research program is the ambient temperature to which participants will be exposed. Two separate protocols will be investigated:
1. Ambient temperature will begin at 23 degrees, and over the course of 90 minutes, will either be increased to 35 degrees or decreased down to 11 degrees. These temperature ramps will be linear and controlled with automatic feedback loop programs within the environmental simulation suite. The cooling and warming exposures will both be carried out by the same participants but on separate days. To allow for further clarification of the thermo-neutral zone (TNZ), participants will have these expired gases measured with indirect hood calorimetry throughout the exposure. Participants will be asked to wear scrubs and sit in a semi-reclined position.
2. During the second protocol, participants will visit the environmental simulation suite for three sessions. Whilst wearing standardised scrubs, they will be asked to live and work inside the room calorimeter for 8 hours in an effort to replicate a normal office day experience. For the control condition, temperature will be kept at the thermo-neutral temperature of 23 degrees. The two intervention exposures will lower the temperature to 18 degrees for the 8 hour exposure or fluctuate the temperature between 23 and 18 throughout the exposure. Indirect room calorimetry will be collected throughout the exposure so that the energy expenditure response to temperature changes may be monitored.
For both protocols, a DXA scan will be performed to gain accurate anthtropometry measurements for subsequent analysis with the calorimetry data. Testing for both protocols will be performed in the Global Energetic Environmental Simulation Suite (GEnESiS), which is situated in the Centre for Translational Physiology at the University of Otago Wellington. Set up and observation will be performed by Mr. Terry O'Donnell, who established the GEnESiS at the centre, and has a history of research and publication in the relationship of metabolism and environment. Due to the cross over design of both protocols, at least a 2 day wash our period will be implemented between exposures.
Intervention code [1] 295994 0
Comparator / control treatment
Participants will serve as their own controls for both protocols with the control conditions being set at 23 degrees. This is a temperature commonly used in the literature by previous studies and has been shown to be in the thermoneutral zone for most participants.
Control group

Primary outcome [1] 299737 0
Changes in energy expenditure as measured with indirect calorimetry
Timepoint [1] 299737 0
This will be continuously measured throughout the exposure interventions.
Secondary outcome [1] 328036 0
Thermal comfort scales will be sought from participants
Timepoint [1] 328036 0
This will be assessed every 15 minutes during protocol 1 and every 30 minutes during protocol 2
Secondary outcome [2] 345593 0
Satiety measures will be sought from participants via questionnaires in protocol two. This questionnaire was designed within our lab, and amended and abridged to be appropriate for this particular study.
Timepoint [2] 345593 0
Questionnaires will be supplied immediately prior to meals (pre-prandial), and thirty minutes post-meals (post-prandial), and at the end of the exposures in protocol two.
Secondary outcome [3] 345594 0
Heart rate will be monitored using the ECG capabilities of the Equivital life sign monitor in protocol one and two .
Timepoint [3] 345594 0
This measures will be taken continuously within each exposure for both protocols.
Secondary outcome [4] 345595 0
Biomarkers of satiety/appetite (ghrelin and des-acyl ghrelin) in blood plasma obtained by venous-puncture blood-draw.
Timepoint [4] 345595 0
Bloods will be taken before and after each exposure in protocol two.
Secondary outcome [5] 345596 0
Breathing rate will be monitored using the expansion-detecting capabilities of the Equivital life sign monitor in protocol one and two.
Timepoint [5] 345596 0
Breathing rate will be monitored continuously within each exposure in protocol two.
Secondary outcome [6] 345597 0
Movement will be assessed using the Equivital life sign monitors tri-axial accelerometer
Timepoint [6] 345597 0
Movement is monitored continuously within each exposure in protocol one and two.
Secondary outcome [7] 345598 0
Skin temperature will be assessed using the Equivital life sign monitor.
Timepoint [7] 345598 0
Skin temperature will be monitored continuously within each exposure for protocol one and two.

Key inclusion criteria
Aged 18-60 years old
Healthy Male or Female
BMI of 18-30
Minimum age
18 Years
Maximum age
60 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Major cardiovascular diseases
Obesity (BMI >30)
Pregnant woman (due to DXA scan)
Prescription medications which may affect autonomic function

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation not concealed.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Order of exposures will be selected by random number generator
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
Multivariable-adjusted general linear models (GLM) will be used to quantify the environmental condition differences in total energy expenditure and the changes in total energy expenditure. In the latter GLM for analysis of changes, covariates will include baseline total energy expenditure and other variables known to be associated with this outcome variable. These covariates will include body composition, neuroendocrine function, gender, age and both peripheral and core temperature. The precise relationship between total energy expenditure and body mass will be identified with an allometric model rather than simple ratio normalisation.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 8324 0
New Zealand
State/province [1] 8324 0

Funding & Sponsors
Funding source category [1] 294724 0
Name [1] 294724 0
Wellington Medical Research Foundation
Address [1] 294724 0
PO BOX 51211
Wellington 5249
Country [1] 294724 0
New Zealand
Primary sponsor type
Terry O'Donnell
University of Otago Wellington
Centre for Translational Physiology
23A Mein Street
Newtown 6021
New Zealand
Secondary sponsor category [1] 293567 0
Name [1] 293567 0
Address [1] 293567 0
Country [1] 293567 0

Ethics approval
Ethics application status
Ethics committee name [1] 296142 0
Central Health and Disability Ethics Committee
Ethics committee address [1] 296142 0
Ministry of Health
Freyberg Building
20 Aitken Street
PO BOX 5013
Wellington 6011
Ethics committee country [1] 296142 0
New Zealand
Date submitted for ethics approval [1] 296142 0
Approval date [1] 296142 0
Ethics approval number [1] 296142 0

Brief summary
Our energy expenditure has three major components; the thermic effect of physical activity, the thermic effect of feeding, and the resting metabolic rate (RMR). This RMR is a basal use of energy for the body to maintain basic functions, such as homeostatic mechanisms.

There is a long-established relationship between ambient temperature and energy expenditure. The range of temperatures where the body naturally maintains its optimum temperature is the thermo-neutral zone (TNZ). This is said to be around 22 °C when light clothing is taken into consideration, and within the individual is determined by insulation, body composition, genetics, and long-term residential environment. Thermo-regulation - an active homeostatic mechanism by which optimum body temperature is maintained - must be employed outside of the TNZ. Previously, mild cold exposure (19 °C) has been shown to induce a ~6% increase in energy expenditure compared to the thermo-neutral (24 °C) control[1]. This corresponded to ~120 kcal/day increase; similar prolonged changes in energy balance have been shown to effect gradual weight change[2].

Modern lifestyle, often revolving around office environments and related environmental control, limit exposures to temperature ‘extremes’ outside of the TNZ. This could limit energy expenditure, complicating weight management in already low-ambulatory jobs. Similarly, increased energy expenditure hypothesized to occur in cold or poorly insulated housing could drive compensatory increases in appetite and subsequent weight management issues.

This study aims to define the TNZ of New Zealand based individuals (protocol one). The TNZ will be used to establish the effect and feasibility of minor decreases or fluctuations in ambient temperature as an intervention to increase energy expenditure and aid in weight management (protocol two). This is pertinent as the only alternative, safe way of increasing energy expenditure is increased physical activity, which is not always an option. Along with continuous physiological measures and body composition information, we may also be able to establish models to determine individual TNZ ranges and energy expenditure under known conditions.

This study will provide potential interventions regarding the obesity epidemic and weight management with New Zealand specific parameters, and suggest a method for its application elsewhere. It may also advise the public health sector as to a further effect of cold housing on physical health.

[1] Celi FS, Brychta RJ, Linderman JD, Butler PW, Alberobello AT, Smith S, Courville AB, Lai EW, Costello R, Skarulis MC, Csako G. Minimal changes in environmental temperature result in a significant increase in energy expenditure and changes in the hormonal homeostasis in healthy adults. European journal of endocrinology. 2010 Dec 1;163(6):863-72.
[2] Hill JO, Wyatt HR, Reed GW, Peters JC. Obesity and the environment: where do we go from here?. Science. 2003 Feb 7;299(5608):853-5.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 69018 0
Mr Terry O'Donnell
Address 69018 0
University of Otago Wellington
Centre for Translational Physiology
23A Mein Street
Wellington 6021
Country 69018 0
New Zealand
Phone 69018 0
+64 4 8061504
Fax 69018 0
Email 69018 0
Contact person for public queries
Name 69019 0
Mr Terry O'Donnell
Address 69019 0
University of Otago Wellington
Centre for Translational Physiology
23A Mein Street
Wellington 6021
Country 69019 0
New Zealand
Phone 69019 0
+64 4 8061504
Fax 69019 0
Email 69019 0
Contact person for scientific queries
Name 69020 0
Mr Terry O'Donnell
Address 69020 0
University of Otago Wellington
Centre for Translational Physiology
23A Mein Street
Wellington 6021
Country 69020 0
New Zealand
Phone 69020 0
+64 4 8061504
Fax 69020 0
Email 69020 0

No information has been provided regarding IPD availability
Summary results
No Results