FastingGlycoFast84NCT07692646
The Effect of Fasting on Peak Fat Oxidation, Mitochondrial Coupling and Extracellular Matrix
A study testing Diet in people with Fasting and Obesity (BMI>30), run by University of Copenhagen at 1 site in Denmark.
Trial summary
The interventional study will recruit four groups (n=10 per group): Young men and women with normal weight (BMI 18-25), and young men and women with obesity (BMI >30). The study will investigate the effect of 84 hours of fasting on peak fat oxidation, mitochondrial coupling and the extracellular matrix. Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Fasting, Obesity (BMI>30), Sex Difference
- What is being tested?
- Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteDenmark
- Study dates
- Jun 2026to Dec 2033
- 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 18 to 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy normal weight men aged [18,40] and BMI [18,25]
- Healthy normal weight women [18,40] and BMI [18,25]
- Healthy obese men [18,40] and BMI [30,40]
- Healthy obese women [18,40] and BMI [30,40]
Who cannot join
- Present or former cardiovascular disease and chronical inflammatory disease
- Consumption of medications and supplements that influence substrate use at rest and/or during exercise
- Pregnancy
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Denmark1 site, 1 recruiting
- Recruiting
Department of Biomedical Sciences
Copenhagen, 2200
Jørn W Helge, PhD, +4528757506, jhelge@sund.ku.dk
About this study
Official title: The Effect of Fasting on Peak Fat Oxidation, Mitochondrial Coupling and Extracellular Matrix in Healthy Men and Lean and Obese Men and Women
The interventional study will recruit four groups (n=10 per group): Young men and women with normal weight (BMI 18-25), and young men and women with obesity (BMI >30). The study will investigate the effect of 84 hours of fasting on peak fat oxidation, mitochondrial coupling and the extracellular matrix.
Read the detailed description
Four groups of young normal weight men (n=10) and women (n=10) and young obese men (n=10) and women (10) are recruited. After verbal and written information is provided signed consent is obtained.
Prior to the first day of the trial, the participants must complete a four-day dietary and exercise record based on the weighing of all food and beverages consumed and tracking all exercise. This is used to asses the participant's habitual diet and activity level. For female participants, an additional form must be completed regarding their menstrual cycle and form of contraception.
On the two trial days (before and after fasting), participants arrive at the laboratory in the morning, and on the first day, the participant will have fasted since the previous evening. Furthermore, participants have been asked to minimize strenous physical activity for 24 hours leading up to testing. Prior to day 1, participants have been instructed to consume a habitual carbohydrate-rich diet for the 48 hours preceding the first test day.
Initially, the participants' body composition is determined by DXA, after which the participants rest for 15 minutes. Subsequently, blood pressure is measured in the supine position whereafter resting energy expenditure is measured by indirect calorimetry. A venous blood sample is taken from the antecubital vein, as well as a biopsy from the m. vastus lateralis and from the subcutaneous abdominal adipose tissue using the Bergström technique applied with suction. After 30 minutes of rest, a graded exercise test on a cycle ergometer is initiated to determine peak fat oxidation and maximal oxygen uptake. After the test is completed and following a minimum of 10 minutes of rest, handgrip strength and knee extension strength are measured. This concludes the test day.
Thereafter, the 84-hour fast is initiated. During the fasting period, the subjects will communicate by telephone each morning with one of the researchers regarding their well-being and any questions they may have. On day 2 subjects will do 1 hour of submaximal exercise. During the fasting subjects will be provided with electrolyte tablets. Following the 84 hours, the subjects return to the laboratory. Here, the same protocol as described above is carried out. This concludes the test day and the experiment.
- Conditions
- Fasting, Obesity (BMI>30), Sex Difference
- Being tested
- Diet
- Keywords
- Muscle metabolism, Mitochondrial coupling, Extracellular matrix composition, Peak fat oxidation
- Medical subject headings
- Fasting, Obesity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
DietOther
Long-term fasting (84 hours), physiological testing before and after fasting: sampling of blood, abdominal adipose tissue and skeletal muscle for molecular analysis and respiratory measurements at rest.
| Study group | Role | What they receive |
|---|---|---|
| Young normal weight men | Experimental | BMI [18, 25] Age [18, 40] Receives: Other: Diet |
| Young normal weight women | Experimental | BMI [18, 25] Age [18, 40] Receives: Other: Diet |
| Young obese men | Experimental | BMI [30, 40] Age [18, 40] Receives: Other: Diet |
| Young obese women | Experimental | BMI [30, 40] Age [18, 40] Receives: Other: Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
The effect of fasting and obesity on protein glycosylation of the extracellular matrix in adipose tissue
The composition and protein glycosylation of the extracellular matrix will be measured in abdominal subcutaneous adipose tissue samples in 20 healthy normal weight men and women and 20 healthy obese men and women.
Measured: The fasting will last approximately 84 hours.
Secondary outcomes (1)
The effect of fasting and obesity on peak fat oxidation
40 participants (20 healthy normal weight men and women and 20 healthy obese men and women) will fast for 84 hours. Before and after the fast, peak fat oxidation (mg fat/min) is measured in an incremental bike test using indirect calorimetry.
Measured: The fasting will last approximately 84 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Jul 2026
- Study startJun 2026 (estimated)
- Primary completionAug 2027 (estimated)
- Study completionDec 2033 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for FastingStudies of the same condition, open and under way.
- More trials run by University of CopenhagenThe sponsor's other registered studies.
- 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
- Non-randomised
- Intervention model
- Parallel groups
- Model description
- Cross sectional study including four groups
- Masking
- None (open label)
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Copenhagen
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Jørn Wulff Helge, University of Copenhagen
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07692646
- Sponsor's protocol ID
- Molecular Memory of Obesity
- Acronym
- GlycoFast84
- Status last verified
- Jun 2026
- First submitted
- 19 Jun 2026
- Last updated
- 9 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: When the experiments are concluded and the paper(s) are accepted that data will be able upon reasonable request
Study at a glance
From the registry record, last updated by the sponsor on 9 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of Fasting on Peak Fat Oxidation, Mitochondrial Coupling and Extracellular Matrix in Healthy Men and Lean and Obese Men and Women
- ClinicalTrials.gov ID
- NCT07692646
- Acronym / sponsor ID
- GlycoFast84 / Molecular Memory of Obesity
- Conditions
- Fasting, Obesity (BMI>30), Sex Difference
- Keywords
- Muscle metabolism, Mitochondrial coupling, Extracellular matrix composition, Peak fat oxidation
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- University of CopenhagenUniversity, hospital or other
- Study start
- Jun 2026 (estimated)
- Primary completion
- Aug 2027 (estimated)
- Study completion
- Dec 2033 (estimated)
- First posted
- 9 Jul 2026 (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.
The interventional study will recruit four groups (n=10 per group): Young men and women with normal weight (BMI 18-25), and young men and women with obesity (BMI >30). The study will investigate the effect of 84 hours of fasting on peak fat oxidation, mitochondrial coupling and the extracellular matrix.
Detailed description
Four groups of young normal weight men (n=10) and women (n=10) and young obese men (n=10) and women (10) are recruited. After verbal and written information is provided signed consent is obtained.
Prior to the first day of the trial, the participants must complete a four-day dietary and exercise record based on the weighing of all food and beverages consumed and tracking all exercise. This is used to asses the participant's habitual diet and activity level. For female participants, an additional form must be completed regarding their menstrual cycle and form of contraception.
On the two trial days (before and after fasting), participants arrive at the laboratory in the morning, and on the first day, the participant will have fasted since the previous evening. Furthermore, participants have been asked to minimize strenous physical activity for 24 hours leading up to testing. Prior to day 1, participants have been instructed to consume a habitual carbohydrate-rich diet for the 48 hours preceding the first test day.
Initially, the participants' body composition is determined by DXA, after which the participants rest for 15 minutes. Subsequently, blood pressure is measured in the supine position whereafter resting energy expenditure is measured by indirect calorimetry. A venous blood sample is taken from the antecubital vein, as well as a biopsy from the m. vastus lateralis and from the subcutaneous abdominal adipose tissue using the Bergström technique applied with suction. After 30 minutes of rest, a graded exercise test on a cycle ergometer is initiated to determine peak fat oxidation and maximal oxygen uptake. After the test is completed and following a minimum of 10 minutes of rest, handgrip strength and knee extension strength are measured. This concludes the test day.
Thereafter, the 84-hour fast is initiated. During the fasting period, the subjects will communicate by telephone each morning with one of the researchers regarding their well-being and any questions they may have. On day 2 subjects will do 1 hour of submaximal exercise. During the fasting subjects will be provided with electrolyte tablets. Following the 84 hours, the subjects return to the laboratory. Here, the same protocol as described above is carried out. This concludes the test day and the experiment.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 4
- Model description
- Cross sectional study including four groups
| Arm | Type | Receives |
|---|---|---|
| Young normal weight men | Experimental | Other: DietBMI [18, 25] Age [18, 40] |
| Young normal weight women | Experimental | Other: DietBMI [18, 25] Age [18, 40] |
| Young obese men | Experimental | Other: DietBMI [30, 40] Age [18, 40] |
| Young obese women | Experimental | Other: DietBMI [30, 40] Age [18, 40] |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Healthy normal weight men aged [18,40] and BMI [18,25]
- Healthy normal weight women [18,40] and BMI [18,25]
- Healthy obese men [18,40] and BMI [30,40]
- Healthy obese women [18,40] and BMI [30,40]
Key exclusion criteria (3 listed)
- Present or former cardiovascular disease and chronical inflammatory disease
- Consumption of medications and supplements that influence substrate use at rest and/or during exercise
- Pregnancy
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 |
|---|---|---|
| DietLong-term fasting (84 hours), physiological testing before and after fasting: sampling of blood, abdominal adipose tissue and skeletal muscle for molecular analysis and respiratory measurements at rest. | Other | Young normal weight men, Young normal weight women, Young obese men, Young obese women |
Primary outcome
The effect of fasting and obesity on protein glycosylation of the extracellular matrix in adipose tissue
Time frame: The fasting will last approximately 84 hours.
The composition and protein glycosylation of the extracellular matrix will be measured in abdominal subcutaneous adipose tissue samples in 20 healthy normal weight men and women and 20 healthy obese men and women.
1 secondary outcome
The effect of fasting and obesity on peak fat oxidation
Time frame: The fasting will last approximately 84 hours
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 9 Jul 2026.
- Individual participant dataSharing planned: Yes. When the experiments are concluded and the paper(s) are accepted that data will be able upon reasonable request
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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.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Diet in people with Fasting and Obesity (BMI>30), run by University of Copenhagen 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 4 inclusion and 3 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: looking for participants now, as of the sponsor's last update on 9 Jul 2026. 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. 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?
Contact Jørn W Helge, PhD (+4528757506, jhelge@sund.ku.dk), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
The effect of fasting and obesity on protein glycosylation of the extracellular matrix in adipose tissue (time frame: The fasting will last approximately 84 hours.). 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 9 Jul 2026.