Obesity and OverweightNCT06684834
Intermittent Carbohydrate Restriction in Cardiometabolic Health
A study testing 5:2 carbohydrate restriction and Early time-restricted carbohydrate intake in people with Obesity and Overweight, run by University of Bath at 1 site in United Kingdom.
Trial summary
Metabolic conditions, such as heart disease, type 2 diabetes, and metabolic syndrome, are among the leading causes of disability and mortality worldwide. Identifying innovative lifestyle strategies to reduce metabolic risk remains a public health priority. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Obesity and Overweight
- What is being tested?
- 5:2 carbohydrate restriction and Early time-restricted carbohydrate intake
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 5 Sep 2023to 1 Oct 2025
- 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
- Waist circumference of ≥94 cm (37 inches) if male and ≥80 cm (31.5 inches) if female, or BMI above 25 kg/m2
- Fat mass index (FMI) of >6 kg/m2 for males, and >9 kg/m2 for females
- Aged between 18-65 years
- Has maintained a stable weight in the last three months (<3% change in body mass)
- Keeps track of menstrual cycle regularity or oral contraceptive use (females only)
Who cannot join
- Has a body weight of ≥120kg
- Plans to undertake other lifestyle modifications during the study to manage weight (e.g. changes in dietary intake or activity levels)
- Current or previous eating disorder
- Diagnosed with major chronic conditions (e.g. type 2 diabetes, coronary heart disease, cancer, chronic kidney disease, etc.)
- Use of medication that may interfere with study outcomes (e.g. glucose or lipid lowering medications)
- Currently or recently pregnant (within last 6 months), planning to get pregnant or currently lactating
Show all 11Show fewer
- Has donated more than 500ml of blood in the last 3 months prior to the initial laboratory visit
- Insufficient mental capacity or language skills to independently understand and follow the study protocol
- Dietary restrictions to ingredients in test meals (e.g. gluten and lactose)
- Has an irregular sleeping pattern (e.g. due to undertaking night-shift work)
- Any condition, concurrent intervention or behaviour deemed either to pose undue personal risk to the participant or to introduce bias into the experiment
Trial locations and contacts
1 site in 1 country.
About this study
Official title: The Effects of Intermittent Carbohydrate Restriction on Metabolic Health and Energy Balance in Adults With Abdominal Overweight and Obesity
Metabolic conditions, such as heart disease, type 2 diabetes, and metabolic syndrome, are among the leading causes of disability and mortality worldwide. Identifying innovative lifestyle strategies to reduce metabolic risk remains a public health priority. Further research is essential to understand how low carbohydrate intake influences human metabolism and how intermittent carbohydrate restriction impacts weight loss and metabolic health markers.
This study will investigate two interventions that restrict dietary carbohydrate intake on different schedules, examining their effects on metabolic health and energy balance in adults with abdominal overweight or obesity. The physiological mechanisms potentially underlying these effects will be explored by measuring a range of lifestyle and metabolic health parameters in both free-living and laboratory settings. A digital behaviour-change intervention will be incorporated after the dietary intervention to assess whether any metabolic effects can be sustained over time.
Read more
The study employs a three-arm parallel-group design consisting of a two-week lifestyle monitoring phase, a four-week dietary intervention, and a four-week digital intervention, with four laboratory visits throughout each phase. During the dietary intervention, participants will be allocated to one of three groups: (i) carbohydrate restriction (<8% of energy intake) on two consecutive days per week, (ii) carbohydrate restriction after 4 pm each day, or (iii) no dietary changes.
Dietary intake, physical activity, and glucose levels will be monitored through wearable devices in free-living conditions. The digital intervention will use a mobile health application that provides individualised lifestyle recommendations and education based on data collected in free-living conditions. Laboratory-based measures will include anthropometry, body composition scans, indirect calorimetry, blood pressure monitoring, fat biopsies, and postprandial sampling of blood and expired air.
- Conditions
- Obesity and Overweight
- Being tested
- 5:2 carbohydrate restriction, Early time-restricted carbohydrate intake
- Keywords
- carbohydrate restriction, carbohydrate timing, intermittent carbohydrate restriction, intermittent energy restriction, evening carbohydrate restriction, carbohydrate periodisation
- Medical subject headings
- Obesity, Overweight
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
5:2 carbohydrate restrictionOther
Carbohydrate ingestion restricted to <8% of energy intake on 2 self-selected consecutive days each week over 28-30 days. Ad libitum dietary amount, type and pattern followed on the remaining 5 days each week.
Early time-restricted carbohydrate intakeOther
Carbohydrate intake restricted to <8% of energy intake after 4pm each day for 28 days. Ad libitum dietary amount, type and pattern followed before 4pm.
| Study group | Role | What they receive |
|---|---|---|
| 5:2 carbohydrate restriction (5:2CR) | Experimental | Laboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. Receives: Other: 5:2 carbohydrate restriction |
| Early time-restricted carbohydrate intake (eTRC) | Experimental | Laboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. Receives: Other: Early time-restricted carbohydrate intake |
| Lifestyle maintenance (control) | No intervention | Laboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Post Prandial Triglyceride Area Under the Curve (AUC)
Plasma triglyceride concentrations assessed postprandially for 5 hours after a mixed meal test
Measured: Pre and post intervention (4 weeks)
Secondary outcomes (12)
Fat Mass
Measured in kilogrammes using Dual Energy X-ray Absorptiometry
Measured: Pre and post intervention (4 weeks)
Lean Body Mass
Measured in kilogrammes using Dual Energy X-ray Absorptiometry
Measured: Pre and post intervention (4 weeks)
Fasting and Post Prandial Glucose Concentration
Plasma glucose concentrations assessed after an overnight fast, postprandially for 5 hours after a mixed meal test
Measured: Pre and post intervention (4 weeks)
Fasting and Post Prandial Insulin Concentration
Plasma insulin concentrations assessed after an overnight fast, postprandially for 5 hours after a mixed meal test
Measured: Pre and post intervention (4 weeks)
Fasting and Post Prandial NEFA Concentration
Plasma NEFA concentrations assessed after an overnight fast, postprandially for 5 hours after a mixed meal test
Measured: Pre and post intervention (4 weeks)
Fasting Triglyceride Concentration
Plasma triglyceride concentrations assessed after an overnight fast
Measured: Pre and post intervention (4 weeks)
Fasting Total Cholesterol Concentration
Assessed after an overnight fast
Measured: Pre and post intervention (4 weeks)
Fasting LDL-C Concentration
Assessed after an overnight fast
Measured: Pre and post intervention (4 weeks)
Fasting HDL-C Concentration
Assessed after an overnight fast
Measured: Pre and post intervention (4 weeks)
Substrate Oxidation
Carbohydrate and fat oxidation rates will be measured using indirect calorimetry at rest and every hour postprandially
Measured: Pre and post intervention (4 weeks)
Adipose Tissue Gene Expression
Expression of several genes related to energy metabolism in adipose biopsies using real-time polymerase chain reaction (RT-PCR)
Measured: Pre and post intervention (4 weeks)
Adipose Tissue Protein Expression
Expression of several proteins related to energy metabolism in adipose biopsies using Western blot
Measured: Pre and post intervention (4 weeks)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 Nov 2024
- Study start5 Sep 2023
- Primary completion1 Oct 2025
- Study completion1 Oct 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Obesity and OverweightStudies 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
- Model description
- A randomised, three-arm parallel-group study
- Masking
- None (open label)
- Enrolment
- 40 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Bath
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Guoda Karoblyte, University of Bath
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06684834
- Sponsor's protocol ID
- 323721
- Status last verified
- Aug 2026
- First submitted
- 24 Oct 2024
- Last updated
- 12 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 12 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effects of Intermittent Carbohydrate Restriction on Metabolic Health and Energy Balance in Adults With Abdominal Overweight and Obesity
- ClinicalTrials.gov ID
- NCT06684834
- Acronym / sponsor ID
- 323721
- Conditions
- Obesity and Overweight
- Keywords
- carbohydrate restriction, carbohydrate timing, intermittent carbohydrate restriction, intermittent energy restriction, evening carbohydrate restriction, carbohydrate periodisation
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 40 participants (actual)
- Lead sponsor
- University of BathUniversity, hospital or other
- Study start
- 5 Sep 2023 (actual)
- Primary completion
- 1 Oct 2025 (actual)
- Study completion
- 1 Oct 2025 (actual)
- First posted
- 12 Nov 2024 (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.
Metabolic conditions, such as heart disease, type 2 diabetes, and metabolic syndrome, are among the leading causes of disability and mortality worldwide. Identifying innovative lifestyle strategies to reduce metabolic risk remains a public health priority. Further research is essential to understand how low carbohydrate intake influences human metabolism and how intermittent carbohydrate restriction impacts weight loss and metabolic health markers.
This study will investigate two interventions that restrict dietary carbohydrate intake on different schedules, examining their effects on metabolic health and energy balance in adults with abdominal overweight or obesity. The physiological mechanisms potentially underlying these effects will be explored by measuring a range of lifestyle and metabolic health parameters in both free-living and laboratory settings. A digital behaviour-change intervention will be incorporated after the dietary intervention to assess whether any metabolic effects can be sustained over time.
The study employs a three-arm parallel-group design consisting of a two-week lifestyle monitoring phase, a four-week dietary intervention, and a four-week digital intervention, with four laboratory visits throughout each phase. During the dietary intervention, participants will be allocated to one of three groups: (i) carbohydrate restriction (<8% of energy intake) on two consecutive days per week, (ii) carbohydrate restriction after 4 pm each day, or (iii) no dietary changes.
Dietary intake, physical activity, and glucose levels will be monitored through wearable devices in free-living conditions. The digital intervention will use a mobile health application that provides individualised lifestyle recommendations and education based on data collected in free-living conditions. Laboratory-based measures will include anthropometry, body composition scans, indirect calorimetry, blood pressure monitoring, fat biopsies, and postprandial sampling of blood and expired air.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- A randomised, three-arm parallel-group study
| Arm | Type | Receives |
|---|---|---|
| 5:2 carbohydrate restriction (5:2CR) | Experimental | Other: 5:2 carbohydrate restrictionLaboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. |
| Early time-restricted carbohydrate intake (eTRC) | Experimental | Other: Early time-restricted carbohydrate intakeLaboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. |
| Lifestyle maintenance (control) | No intervention | –Laboratory measurements will be obtained before and after the intervention. Physical activity, dietary intake and interstitial glucose concentrations will be monitored in free-living conditions throughout the intervention. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Waist circumference of ≥94 cm (37 inches) if male and ≥80 cm (31.5 inches) if female, or BMI above 25 kg/m2
- Fat mass index (FMI) of >6 kg/m2 for males, and >9 kg/m2 for females
- Aged between 18-65 years
- Has maintained a stable weight in the last three months (<3% change in body mass)
- Keeps track of menstrual cycle regularity or oral contraceptive use (females only)
Key exclusion criteria (11 listed)
- Has a body weight of ≥120kg
- Plans to undertake other lifestyle modifications during the study to manage weight (e.g. changes in dietary intake or activity levels)
- Current or previous eating disorder
- Diagnosed with major chronic conditions (e.g. type 2 diabetes, coronary heart disease, cancer, chronic kidney disease, etc.)
- Use of medication that may interfere with study outcomes (e.g. glucose or lipid lowering medications)
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 |
|---|---|---|
| 5:2 carbohydrate restrictionCarbohydrate ingestion restricted to <8% of energy intake on 2 self-selected consecutive days each week over 28-30 days. Ad libitum dietary amount, type and pattern followed on the remaining 5 days each week. | Other | 5:2 carbohydrate restriction (5:2CR) |
| Early time-restricted carbohydrate intakeCarbohydrate intake restricted to <8% of energy intake after 4pm each day for 28 days. Ad libitum dietary amount, type and pattern followed before 4pm. | Other | Early time-restricted carbohydrate intake (eTRC) |
Primary outcome
Post Prandial Triglyceride Area Under the Curve (AUC)
Time frame: Pre and post intervention (4 weeks)
Plasma triglyceride concentrations assessed postprandially for 5 hours after a mixed meal test
12 secondary outcomes
Fat Mass
Time frame: Pre and post intervention (4 weeks)
Lean Body Mass
Time frame: Pre and post intervention (4 weeks)
Fasting and Post Prandial Glucose Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting and Post Prandial Insulin Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting and Post Prandial NEFA Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting Triglyceride Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting Total Cholesterol Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting LDL-C Concentration
Time frame: Pre and post intervention (4 weeks)
Fasting HDL-C Concentration
Time frame: Pre and post intervention (4 weeks)
Substrate Oxidation
Time frame: Pre and post intervention (4 weeks)
Adipose Tissue Gene Expression
Time frame: Pre and post intervention (4 weeks)
Adipose Tissue Protein Expression
Time frame: Pre and post intervention (4 weeks)
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 12 Aug 2026.
- Individual participant dataSharing planned: Undecided
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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 5:2 carbohydrate restriction and Early time-restricted carbohydrate intake in people with Obesity and Overweight, run by University of Bath at 1 site in United Kingdom.
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 5 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 12 Aug 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 United Kingdom. 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?
Post Prandial Triglyceride Area Under the Curve (AUC) (time frame: Pre and post intervention (4 weeks)). 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 12 Aug 2026.