Adipose Tissue, BrownWinterBATNCT03541096
Winter-Swimming and Brown Adipose Tissue Activity in Middel-aged Obese Subjects (WinterBAT).
A study testing Winter Swimming in people with Adipose Tissue, Brown and Brown Adipose Tissue, run by Kristian Karstoft at 1 site in Denmark.
Trial summary
This study investigates repetitive cold-water exposure on brown fat activity assessed by PET/CT scanning. Furthermore we will assess glucose control upon winter-swimming. Obese prediabetic men and women will be randomized to winter-swimming or control conditions for 4 months. Read more about this study
- Who is it for?
- Ages 40 years and older
- Conditions the study is for
- Adipose Tissue, Brown, Brown Adipose Tissue, Uncoupling Protein 1
- What is being tested?
- Winter Swimming
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 30 participants
- Where
- 1 siteDenmark
- Study dates
- 7 Nov 2018to 31 Dec 2025
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 40 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Waist circumference above 80 cm for women and 94 cm for men.
- BMI > 25 but <40 kg/m2
- Age > 40 years.
- Low to moderate physical activity level (no physical activity or on average 30 minutes of moderate physical activity per day and not more than 3 hours of training pr. Week)
- Subjects will be included in either one of these cases after the screening:
- Fasting plasma glucose above 5.6 millimol per liter (mmoL/L).
- HbA1C >39 millimol per mol (mmol/mol).
- 2 hour plasma glucose after a 75 g. oral glucose tolerance test (OGTT) above 7.8 mmol/L.
Who cannot join
- Winter swimmer
- Any history of Cancer,
- Clinically significant liver, kidney, heart, inflammatory or lung-disease.
- Pregnancy
- Taking medication (not for hay fever), including glucose-lowering treatment.
- HbA1c >55 mmol/mol and/or 2-h plasma glucose in the 75-g OGTT > 15 mmol/L, fasting plasma glucose above 6.9.
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- Iron deficiency
- Increased International Normalised Ratio for coagulation (INR).
- Femoral hernia, vene prostheses (pants prosthesis), thrombs in v. Femoralis.
- Abnormal ultrasound echocardiography of the heart found at the health-examination day.
- Contraindications to cold exposure including severe Raynauds disease.
- History of alcohol abuse or use of more than 14 units pr. Week.
- History of drug abuse, including marihuana.
- Smoking including occasional smoking.
- Pacemaker or other electronics implanted in the body.
- Claustrophobia, communication problems, including understanding the experimental protocol.
- History of contrast allergy.
Trial locations and contacts
1 site in 1 country.
Denmark1 site
Center for Inflammation and Metabolism/ Center for Physical Activity Research
Copenhagen, 2100
About this study
Official title: The Impact of Winter Swimming on Brown Adipose Tissue Recruitment and Metabolic Health in Middel-aged Obese Pre-diabetic Subjects.
This study investigates repetitive cold-water exposure on brown fat activity assessed by PET/CT scanning. Furthermore we will assess glucose control upon winter-swimming. Obese prediabetic men and women will be randomized to winter-swimming or control conditions for 4 months.
Read the detailed description
Brown fat (BAT) is an energy-consuming tissue. Long-term activation of BAT in adults increases clearance of blood glucose and non-esterified fatty acids (NEFA), insulin sensitivity and metabolic rate. Moreover, adipokines released from BAT, known as batokines, represent a promising but currently unexplored area in terms of metabolic regulation. Cooling activates BAT; however, current cooling protocols fail to activate BAT in a large part of the population. Whether this failure in activation is related to biology, inefficient detection or cooling protocols is unknown. With our initial acute cooling study (protocol number: H-16038581), these protocols have successfully been optimized whereupon novel batokines will be identified. Having established a methodology for assessing BAT activity and batokine profiles, a longer-term cooling intervention (winter swimming) will be performed to examine the effect of repetitive cold-water exposure on BAT activity. Obese pre-diabetic subjects will be included in a 4-month supervised winter swimming (WS) intervention.
It is hypothesized, that repetitive cold-water exposure constituted by WS, increase BAT activation and volume, followed by improved glycemic control in obese pre-diabetic subjects.
Method The study is a randomized controlled, parallel-group intervention study. The investigator will recruit 30 obese pre-diabetic non-winter-swimmers to participate in a WS intervention group (n=15) or control group (n=15) with no WS activities. Subjects will either be randomized to the WS group, who will winter-swim 4 months, 2-3 times/week including sauna-visits if desired, or control conditions with no WS during the 4 months (October to May).
Main aims
- To assess whether WS will have an immediate effect on BAT recruitment or function.
- To assess whether WS will have an effect on glycemic control.
- Conditions
- Adipose Tissue, Brown, Brown Adipose Tissue, Uncoupling Protein 1, Cold Exposure, Obesity, Type 2 Diabetes Mellitus
- Being tested
- Winter Swimming, Control group
- Medical subject headings
- Obesity, Diabetes Mellitus, Type 2
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Winter SwimmingBehavioural
Supervised Winter Swimming in Copenhagen
Control groupBehavioural
No winter swimming activities.
| Study group | Role | What they receive |
|---|---|---|
| Winter Swimmers | Experimental | 4 Months of supervised winter swimming. Receives: Behavioral: Winter Swimming |
| Control group | Placebo comparator | No winter swimming activities. Receives: Behavioral: Control group |
What is being measured
The primary outcome is the main question the study is designed to answer.
Difference between groups in change in brown adipose tissue (BAT) activity during cooling
BAT activity is measured using positron emission tomography (PET)- Computer tomography (CT) scan. The PET-CT scan uses a glucose-radiotracer (fludeoxyglucose-18 (FDG)) to measure the glucose uptake in BAT, which is associated with BAT activity. FDG is injected following one hour of cooling and the subjects are scanned following one additional hour of cooling. The subjects are continuously cooled throughout the scanning procedure. Difference between groups in change in FDG tracer uptake (post minus pre intervention) during 1,5 hours of cooling is calculated.
Measured: Day 0 (before intervention) and Day 120 (after intervention)
Secondary outcomes (1)
Difference between groups in change in glycemic control
Glycemic control is measured using a 4 hour mixed meal tolerance test. Difference between groups in change in the mean MMTT glucose levels during the MMTT (post minus pre intervention) will be calculated.
Measured: Day 0 (before intervention) and Day 120 (after intervention)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted30 May 2018
- Study start7 Nov 2018
- Primary completion1 Jun 2021
- Study completion31 Dec 2025 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Adipose Tissue, BrownStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Outcomes assessor
- Enrolment
- 30 participants (actual)
Sponsor and investigators
- Lead sponsor
- Kristian Karstoft
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor-investigator, Kristian Karstoft, Copenhagen University Hospital, Rigshospitalet
- Investigators
- Camilla Schéele, PhD, Principal investigator, Copenhagen University Hospital, Rigshospitalet
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03541096
- Sponsor's protocol ID
- H-18015882 WinterBAT-Study
- Acronym
- WinterBAT
- Status last verified
- May 2025
- First submitted
- 17 May 2018
- Last updated
- 17 Aug 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 17 Aug 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Impact of Winter Swimming on Brown Adipose Tissue Recruitment and Metabolic Health in Middel-aged Obese Pre-diabetic Subjects.
- ClinicalTrials.gov ID
- NCT03541096
- Acronym / sponsor ID
- WinterBAT / H-18015882 WinterBAT-Study
- Conditions
- Adipose Tissue, Brown, Brown Adipose Tissue, Uncoupling Protein 1, Cold Exposure, Obesity, Type 2 Diabetes Mellitus
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 30 participants (actual)
- Lead sponsor
- Kristian KarstoftUniversity, hospital or other
- Study start
- 7 Nov 2018 (actual)
- Primary completion
- 1 Jun 2021 (actual)
- Study completion
- 31 Dec 2025 (estimated)
- First posted
- 30 May 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study investigates repetitive cold-water exposure on brown fat activity assessed by PET/CT scanning. Furthermore we will assess glucose control upon winter-swimming. Obese prediabetic men and women will be randomized to winter-swimming or control conditions for 4 months.
Detailed description
Brown fat (BAT) is an energy-consuming tissue. Long-term activation of BAT in adults increases clearance of blood glucose and non-esterified fatty acids (NEFA), insulin sensitivity and metabolic rate. Moreover, adipokines released from BAT, known as batokines, represent a promising but currently unexplored area in terms of metabolic regulation. Cooling activates BAT; however, current cooling protocols fail to activate BAT in a large part of the population. Whether this failure in activation is related to biology, inefficient detection or cooling protocols is unknown. With our initial acute cooling study (protocol number: H-16038581), these protocols have successfully been optimized whereupon novel batokines will be identified. Having established a methodology for assessing BAT activity and batokine profiles, a longer-term cooling intervention (winter swimming) will be performed to examine the effect of repetitive cold-water exposure on BAT activity. Obese pre-diabetic subjects will be included in a 4-month supervised winter swimming (WS) intervention.
It is hypothesized, that repetitive cold-water exposure constituted by WS, increase BAT activation and volume, followed by improved glycemic control in obese pre-diabetic subjects.
Method The study is a randomized controlled, parallel-group intervention study. The investigator will recruit 30 obese pre-diabetic non-winter-swimmers to participate in a WS intervention group (n=15) or control group (n=15) with no WS activities. Subjects will either be randomized to the WS group, who will winter-swim 4 months, 2-3 times/week including sauna-visits if desired, or control conditions with no WS during the 4 months (October to May).
Main aims
- To assess whether WS will have an immediate effect on BAT recruitment or function.
- To assess whether WS will have an effect on glycemic control.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Winter Swimmers | Experimental | Behavioral: Winter Swimming4 Months of supervised winter swimming. |
| Control group | Placebo comparator | Behavioral: Control groupNo winter swimming activities. |
Who may qualify
- Ages
- 40 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (8 listed)
- Waist circumference above 80 cm for women and 94 cm for men.
- BMI > 25 but <40 kg/m2
- Age > 40 years.
- Low to moderate physical activity level (no physical activity or on average 30 minutes of moderate physical activity per day and not more than 3 hours of training pr. Week)
- Fasting plasma glucose above 5.6 millimol per liter (mmoL/L).
Key exclusion criteria (17 listed)
- Winter swimmer
- Any history of Cancer,
- Clinically significant liver, kidney, heart, inflammatory or lung-disease.
- Pregnancy
- Taking medication (not for hay fever), including glucose-lowering treatment.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Winter SwimmingSupervised Winter Swimming in Copenhagen | Behavioural | Winter Swimmers |
| Control groupNo winter swimming activities. | Behavioural | Control group |
Primary outcome
Difference between groups in change in brown adipose tissue (BAT) activity during cooling
Time frame: Day 0 (before intervention) and Day 120 (after intervention)
BAT activity is measured using positron emission tomography (PET)- Computer tomography (CT) scan. The PET-CT scan uses a glucose-radiotracer (fludeoxyglucose-18 (FDG)) to measure the glucose uptake in BAT, which is associated with BAT activity. FDG is injected following one hour of cooling and the subjects are scanned following one additional hour of cooling. The subjects are continuously cooled throughout the scanning procedure. Difference between groups in change in FDG tracer uptake (post minus pre intervention) during 1,5 hours of cooling is calculated.
1 secondary outcome
Difference between groups in change in glycemic control
Time frame: Day 0 (before intervention) and Day 120 (after intervention)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Aug 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Camilla Schéele, PhD principal investigator
Copenhagen University Hospital, Rigshospitalet
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Winter Swimming in people with Adipose Tissue, Brown and Brown Adipose Tissue, run by Kristian Karstoft at 1 site in Denmark.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 17 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 17 Aug 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Denmark. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Difference between groups in change in brown adipose tissue (BAT) activity during cooling (time frame: Day 0 (before intervention) and Day 120 (after intervention)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Aug 2025.