Diet, HealthyGutEnergyNCT06932666
Why Calories Are Not the Same - a Gut Explanation?
A study testing Diet A group and Diet B group in people with Diet, Healthy and Breath Analysis, run by University of Copenhagen at 1 site in Denmark.
Trial summary
The aim of this study is to understand how the gut microbiome influences how much dietary energy humans excrete via feces. This study is based on the hypothesis that levels of methane in exhaled breath represent two different gut microbiome community structures, and therefore influence fecal energy excretion… Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Diet, Healthy, Breath Analysis
- What is being tested?
- Diet A group and Diet B group
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 1 siteDenmark
- Study dates
- 15 May 2025to 13 May 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- 18-65 years old
- BMI:18.5-29.9 kg/m2
- Self-reported regular defecations defined as at least every second day
- Willing to collect urine and stool samples at home and able to temporarily store them in their own freezer in a provided container
- Willing to exclusively eat the food provided
- Owning a smartphone (iOS 11.0 and onwards, or Android 5.0 and onwards) with access to the internet
- Speak and understand Danish or English
Who cannot join
- Current pregnancy or lactation
- Following a specific dietary program or diet (e.g., vegetarian, vegan, gluten-free) or unable to consume the food provided
- Diagnosis of small intestinal bacterial overgrowth (SIBO), inflammatory bowel diseases (IBD), gastrointestinal obstruction, or ischemic colitis
- Diagnosed chronic constipation
- Regular use of diarrhea inhibitors or laxatives
- Any chronic disease that can affect the outcomes of the study
Show all 11Show fewer
- Use of medications potentially altering gastric pH (proton pump inhibitors, histamine receptor antagonists, antacids)
- Use of medications potentially altering the gastro-intestinal motility (prokinetics, antiemetic agents, anticholinergic agents, narcotic analgesics, nonsteroidal anti-inflammatory drugs, peroral glucocorticoids, and GLP-1 related medications such as semaglutide and liraglutide)
- Use of antibiotics, or any medication that can affect any outcomes of the study, within the previous three months
- Concurrent participation in another trial
- Any condition that makes the project responsible and/or the clinical responsible doubt the feasibility of the volunteer's participation
Trial locations and contacts
1 site in 1 country.
Denmark1 site
University of Copenhagen, Department of Nutrition, Exercise and Sports
Frederiksberg, Capital Region, 1958
About this study
Official title: Why Calories Are Not the Same - a Gut Explanation
The aim of this study is to understand how the gut microbiome influences how much dietary energy humans excrete via feces. This study is based on the hypothesis that levels of methane in exhaled breath represent two different gut microbiome community structures, and therefore influence fecal energy excretion differently. Moreover, this study is assessed in the context of two different diets, both isocaloric and equal in macronutrient composition, but differing in contents of fiber, resistant starch, and large particles; which are hypothesized to impact the gut microbiome differently.
Read the detailed description
The trial is a cross-over trial including two controlled isocaloric dietary interventions of three days duration. The two diets are isocaloric but with different contents of fiber, resistant starch, and food particle sizes. Each intervention is separated by a wash-out period of at least 10 days where participants adhere to their habitual diet. The trial includes a total of five visits (one screening visit and four regular visits).
Before the trial, participants undergo a screening period of 4 days. During the 4-day screening period, participants measure the levels of methane in their exhaled breath. Based on median breath methane levels, participants are allocated to one of the two arms: (HMP: high methane producers; LMP: low methane producers). Enrollment in the intervention trial will be conducted so there are similar numbers of participants in both arms.
At the beginning and at the end of each 3-day intervention period, participants consume a blue muffin, containing a royal blue dye that changes the stool color. The appearance of the color in stool following the first muffin will mark the beginning of the stool collection period, which will continue until the stool color change is no longer noticeable following consumption of the second muffin. Therefore, the duration of the stool collection period, which is estimated to be on average 3 days, will ultimately depend on the participants' passage time of food (i.e., intestinal transit time).
During the screening period, participants are asked to:
- measure their methane and hydrogen levels in exhaled breath using a portable device
- report defecation patterns (including stool frequency and Bristol Stool Scale)
Before each intervention period, participants are asked to:
- collect a fecal and urine sample
- register three days of habitual diet
At the visits before each intervention period, the following samples are collected:
- a blood sample
- methane and hydrogen measurements in exhaled breath
- anthropometrics
- data on physical activity
During the intervention periods, participants are asked to:
- exclusively eat all the foods provided
- collect all their stool samples, as specified above
- collect three morning urine samples (one daily for the following three days)
- measure their methane and hydrogen levels in their exhaled breath using a portable device
- report their defecation patterns and gastrointestinal symptoms
- Conditions
- Diet, Healthy, Breath Analysis
- Being tested
- Diet A group, Diet B group
- Keywords
- Fecal energy, Metabolizable energy, Breath methane, Gut microbiome, Metabolomics, Dietary fiber, Resistant starch, Food particle size
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Diet A groupOther
Diet high in fiber (> 40g/10MJ), high in resistant starch (> 10g/10MJ), and containing large food particles. Diet is provided for 3 full days, consists of three meals per day (breakfast, lunch, and dinner) and in-between meals, and covers 100% of the participants' energy requirements.
Diet B groupOther
Diet low in fiber (< 10g/10MJ), low in resistant starch (< 3g/10MJ) and containing small food particles. Diet is provided for 3 full days, consists of three meals per day (breakfast, lunch, and dinner) and in-between meals, and covers 100% of the participants' energy requirements.
| Study group | Role | What they receive |
|---|---|---|
| High-methane producers | Experimental | Individuals exhaling high levels of methane (median exhaled methane >= 5 ppm), as measured 3-times daily during the screening period. Receives: Other: Diet A group; Other: Diet B group |
| Low-methane producers | Experimental | Individuals exhaling low levels of methane (median exhaled methane < 5 ppm), as measured 3-times daily during the screening period. Receives: Other: Diet A group; Other: Diet B group |
What is being measured
The primary outcome is the main question the study is designed to answer.
Total fecal energy excretion (between high- and low-methane producers)
Differences in total fecal energy excretion, determined as total kilocalories excreted via feces, between low and high methane producers following intake of the two controlled, isocaloric diets.
Measured: During each stool collection period (following each 3-day intervention period)
Secondary outcomes (14)
Total fecal energy excretion (between diet A and diet B)
Differences in total fecal energy excretion, determined as total kilocalories excreted via feces, between the two isocaloric diets (that differ in fiber, resistant starch, and particle size).
Measured: During each stool collection period (following each 3-day intervention period)
Fecal energy density
Differences in fecal energy density, determined as fecal energy (kcal) relative to fecal weight, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Total fecal weight excreted
Differences in total fecal weight excreted, determined as dry weight (grams), between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Breath hydrogen and methane levels
Differences in breath methane and hydrogen concentration in exhaled breath, measured in parts per million (PPM), between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Whole-gut transit time
Differences in whole-gut transit time, determined by the passage time of muffins with blue dye, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Stool consistency
Differences in stool consistency, determined by Bristol Stool Scale, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Stool frequency
Differences in stool frequency, determined by defecation records registered by the participants, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Stool moisture
Differences in stool moisture, determined as fecal water content relative to fecal weight, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Fecal pH
Differences in fecal pH between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Fecal microbial load
Differences in fecal microbial load, determined as total microbial DNA reads in feces, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Fecal host DNA concentration
Differences in fecal host DNA concentration, determined as total human DNA reads in feces, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Fecal short-chain fatty acids
Differences in fecal short-chain fatty acid concentrations between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Gut microbiome composition (16S)
Differences in gut microbiome composition, determined by 16S amplicon sequencing of fecal DNA, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Gut microbiome composition and functions (shotgun sequencing)
Differences in gut microbiome taxonomic composition and functions, determined by shotgun sequencing of fecal DNA, between high- and low-methane producers.
Measured: During each 3-day intervention period and its following stool collection period
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted17 Apr 2025
- Study start15 May 2025
- Primary completion13 May 2026
- Study completion13 May 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Diet, HealthyStudies 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
- Non-randomised
- Intervention model
- Crossover
- Model description
- Overall, there are two parallel arms - high- (HMP) and low- (LMP) methane producers, to which the participants are allocated in a ratio 1:1 after a 4-day screening period, where individual levels of methane in exhaled breath are measured multiple times. In both arms, participants undergo two 3-days dietary interventions in a crossover design and separated by a +10-day washout period. Participants are randomized to receiving diet A first or diet B first. These two diets are isocaloric and equal in macronutrient composition, but differ on dietary fiber, resistant starch and food particle size.
- Masking
- None (open label)
- Enrolment
- 60 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Copenhagen
- Sponsor type
- University, hospital or other
- Collaborators
- Wageningen University and Research
- Responsible party
- Principal investigator, Henrik Munch Roager, University of Copenhagen
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06932666
- Sponsor's protocol ID
- M408
- Acronym
- GutEnergy
- Status last verified
- Jun 2026
- First submitted
- 10 Apr 2025
- Last updated
- 2 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Why Calories Are Not the Same - a Gut Explanation
- ClinicalTrials.gov ID
- NCT06932666
- Acronym / sponsor ID
- GutEnergy / M408
- Conditions
- Diet, Healthy, Breath Analysis
- Keywords
- Fecal energy, Metabolizable energy, Breath methane, Gut microbiome, Metabolomics, Dietary fiber, Resistant starch, Food particle size
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 60 participants (actual)
- Lead sponsor
- University of CopenhagenUniversity, hospital or other
- Collaborators
- Wageningen University and Research
- Study start
- 15 May 2025 (actual)
- Primary completion
- 13 May 2026 (actual)
- Study completion
- 13 May 2026 (actual)
- First posted
- 17 Apr 2025 (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 aim of this study is to understand how the gut microbiome influences how much dietary energy humans excrete via feces. This study is based on the hypothesis that levels of methane in exhaled breath represent two different gut microbiome community structures, and therefore influence fecal energy excretion differently. Moreover, this study is assessed in the context of two different diets, both isocaloric and equal in macronutrient composition, but differing in contents of fiber, resistant starch, and large particles; which are hypothesized to impact the gut microbiome differently.
Detailed description
The trial is a cross-over trial including two controlled isocaloric dietary interventions of three days duration. The two diets are isocaloric but with different contents of fiber, resistant starch, and food particle sizes. Each intervention is separated by a wash-out period of at least 10 days where participants adhere to their habitual diet. The trial includes a total of five visits (one screening visit and four regular visits).
Before the trial, participants undergo a screening period of 4 days. During the 4-day screening period, participants measure the levels of methane in their exhaled breath. Based on median breath methane levels, participants are allocated to one of the two arms: (HMP: high methane producers; LMP: low methane producers). Enrollment in the intervention trial will be conducted so there are similar numbers of participants in both arms.
At the beginning and at the end of each 3-day intervention period, participants consume a blue muffin, containing a royal blue dye that changes the stool color. The appearance of the color in stool following the first muffin will mark the beginning of the stool collection period, which will continue until the stool color change is no longer noticeable following consumption of the second muffin. Therefore, the duration of the stool collection period, which is estimated to be on average 3 days, will ultimately depend on the participants' passage time of food (i.e., intestinal transit time).
During the screening period, participants are asked to:
- measure their methane and hydrogen levels in exhaled breath using a portable device
- report defecation patterns (including stool frequency and Bristol Stool Scale)
Before each intervention period, participants are asked to:
- collect a fecal and urine sample
- register three days of habitual diet
At the visits before each intervention period, the following samples are collected:
- a blood sample
- methane and hydrogen measurements in exhaled breath
- anthropometrics
- data on physical activity
During the intervention periods, participants are asked to:
- exclusively eat all the foods provided
- collect all their stool samples, as specified above
- collect three morning urine samples (one daily for the following three days)
- measure their methane and hydrogen levels in their exhaled breath using a portable device
- report their defecation patterns and gastrointestinal symptoms
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Overall, there are two parallel arms - high- (HMP) and low- (LMP) methane producers, to which the participants are allocated in a ratio 1:1 after a 4-day screening period, where individual levels of methane in exhaled breath are measured multiple times. In both arms, participants undergo two 3-days dietary interventions in a crossover design and separated by a +10-day washout period. Participants are randomized to receiving diet A first or diet B first. These two diets are isocaloric and equal in macronutrient composition, but differ on dietary fiber, resistant starch and food particle size.
| Arm | Type | Receives |
|---|---|---|
| High-methane producers | Experimental | Other: Diet A group, Other: Diet B groupIndividuals exhaling high levels of methane (median exhaled methane >= 5 ppm), as measured 3-times daily during the screening period. |
| Low-methane producers | Experimental | Other: Diet A group, Other: Diet B groupIndividuals exhaling low levels of methane (median exhaled methane < 5 ppm), as measured 3-times daily during the screening period. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- 18-65 years old
- BMI:18.5-29.9 kg/m2
- Self-reported regular defecations defined as at least every second day
- Willing to collect urine and stool samples at home and able to temporarily store them in their own freezer in a provided container
- Willing to exclusively eat the food provided
Key exclusion criteria (11 listed)
- Current pregnancy or lactation
- Following a specific dietary program or diet (e.g., vegetarian, vegan, gluten-free) or unable to consume the food provided
- Diagnosis of small intestinal bacterial overgrowth (SIBO), inflammatory bowel diseases (IBD), gastrointestinal obstruction, or ischemic colitis
- Diagnosed chronic constipation
- Regular use of diarrhea inhibitors or laxatives
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 |
|---|---|---|
| Diet A groupDiet high in fiber (> 40g/10MJ), high in resistant starch (> 10g/10MJ), and containing large food particles. Diet is provided for 3 full days, consists of three meals per day (breakfast, lunch, and dinner) and in-between meals, and covers 100% of the participants' energy requirements. | Other | High-methane producers, Low-methane producers |
| Diet B groupDiet low in fiber (< 10g/10MJ), low in resistant starch (< 3g/10MJ) and containing small food particles. Diet is provided for 3 full days, consists of three meals per day (breakfast, lunch, and dinner) and in-between meals, and covers 100% of the participants' energy requirements. | Other | High-methane producers, Low-methane producers |
Primary outcome
Total fecal energy excretion (between high- and low-methane producers)
Time frame: During each stool collection period (following each 3-day intervention period)
Differences in total fecal energy excretion, determined as total kilocalories excreted via feces, between low and high methane producers following intake of the two controlled, isocaloric diets.
14 secondary outcomes
Total fecal energy excretion (between diet A and diet B)
Time frame: During each stool collection period (following each 3-day intervention period)
Fecal energy density
Time frame: During each 3-day intervention period and its following stool collection period
Total fecal weight excreted
Time frame: During each 3-day intervention period and its following stool collection period
Breath hydrogen and methane levels
Time frame: During each 3-day intervention period and its following stool collection period
Whole-gut transit time
Time frame: During each 3-day intervention period and its following stool collection period
Stool consistency
Time frame: During each 3-day intervention period and its following stool collection period
Stool frequency
Time frame: During each 3-day intervention period and its following stool collection period
Stool moisture
Time frame: During each 3-day intervention period and its following stool collection period
Fecal pH
Time frame: During each 3-day intervention period and its following stool collection period
Fecal microbial load
Time frame: During each 3-day intervention period and its following stool collection period
Fecal host DNA concentration
Time frame: During each 3-day intervention period and its following stool collection period
Fecal short-chain fatty acids
Time frame: During each 3-day intervention period and its following stool collection period
Gut microbiome composition (16S)
Time frame: During each 3-day intervention period and its following stool collection period
Gut microbiome composition and functions (shotgun sequencing)
Time frame: During each 3-day intervention period and its following stool collection period
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Jun 2026.
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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.
The record lists no contact. Use the official record to reach the sponsor.
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 A group and Diet B group in people with Diet, Healthy and Breath Analysis, 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 7 inclusion and 11 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: finished, as of the sponsor's last update on 2 Jun 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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
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?
Total fecal energy excretion (between high- and low-methane producers) (time frame: During each stool collection period (following each 3-day intervention period)). 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 2 Jun 2026.