HealthyNCT07056465
Exploring Adherence and Acceptability of an Intermittent Carbohydrate Restriction Regime in Free-Living Adults: A Feasibility Study
A study testing Intermittent Carbohydrate Restriction (ICR) Protocol in people with Healthy, run by University of Surrey at 1 site in United Kingdom.
Trial summary
This study investigates a novel dietary approach called Intermittent Carbohydrate Restriction (ICR), which involves reducing carbohydrate intake on selected days of the week while allowing habitual eating on other days. Read more about this study
- Who is it for?
- Ages 18 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy
- What is being tested?
- Intermittent Carbohydrate Restriction (ICR) Protocol
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 37 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 13 Jan 2023to 20 Apr 2024
- 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 60 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Body Mass Index (BMI) between 18.5 and 29.9 kg/m² (normal to overweight range; avoids confounding from obesity-related metabolic disturbances).
- Generally healthy (self-reported good health with no diagnosed metabolic, cardiovascular, or endocrine disorders).
- Not currently following a weight-loss diet or carbohydrate-restricted diet (to ensure dietary baseline is not already influenced by similar patterns).
- Willing and able to follow the ICR protocol for 4 weeks (includes ability to prepare meals and follow dietary instructions independently).
- Able to attend in-person laboratory assessments at baseline and follow-up (for measurements of REE, body composition, etc.).
- Fluent in English (to ensure comprehension of dietary instructions, consent forms, and interviews).
- Provides written informed consent (as per ethical standards and good clinical practice).
Who cannot join
- Diagnosed metabolic or endocrine disorders (e.g., diabetes, hypothyroidism, PCOS), to avoid confounding effects on metabolic outcomes and dietary adherence.
- History of cardiovascular disease, renal disease, or gastrointestinal disorders (e.g., IBS, coeliac disease), which may affect dietary tolerance or nutrient absorption.
- Currently pregnant, breastfeeding, or planning pregnancy during the study (due to potential risks and altered metabolic/nutritional needs).
- BMI <18.5 or ≥30 kg/m² (to exclude underweight or obese individuals where safety and generalizability may differ).
- Currently following a restrictive or structured diet (e.g., ketogenic, low-carb, intermittent fasting, or weight-loss diets), to ensure a clear baseline dietary behavior.
- History or presence of eating disorders (e.g., anorexia nervosa, bulimia, binge eating), for participant safety and ethical considerations.
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- Use of medications or supplements known to affect metabolism or appetite (e.g., corticosteroids, GLP-1 agonists, weight-loss medications).
- Smoking or excessive alcohol consumption (defined as >14 units/week), which may interfere with dietary adherence and metabolic assessments.
- Participation in another clinical or dietary study within the past 3 months (to avoid overlapping interventions or residual effects).
- Inability or unwillingness to comply with study procedures (including dietary tracking, visit attendance, or sample collection).
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Acceptability of, and Compliance to a Novel Intermittent Carbohydrate Restriction Dietary Intervention
This study investigates a novel dietary approach called Intermittent Carbohydrate Restriction (ICR), which involves reducing carbohydrate intake on selected days of the week while allowing habitual eating on other days. Previous research suggests that intermittent dietary strategies may improve metabolic health and support better adherence compared to continuous calorie restriction.
In this single-arm feasibility study, 40 healthy adults will follow the ICR protocol for 4 weeks. Outcomes including body weight, body fat percentage, waist circumference, and resting metabolic rate will be measured before and after the intervention. Dietary adherence, changes in habitual intake, and participant experiences will be assessed through food diaries, 24-hour recalls, questionnaires, and exit interviews.
The primary aim is to evaluate the acceptability and adherence to the ICR protocol in free-living conditions. Secondary aims include exploring its effects on body composition and diet-related behaviours, with the goal of informing future long-term dietary interventions.
Read the detailed description
Intermittent energy restriction (IER) has shown to improve postprandial metabolic systems and cognitive function, with superiority in dietary adherence compared with continuous energy restriction (CER)(1-3). A gap in current research is the impact of intermittent carbohydrate restriction (ICR) compared with IER in line with the carbohydrate-insulin model. Novel research (UEC 2019 008 FHMS) has explored the acute effects of ICR on postprandial metabolic systems and found engagement of the same underlying mechanisms with superior outcomes in glucose and lipid metabolism, compared with IER. Unpublished data supports the superiority of ICR over IER in dietary adherence due to perceived increased flexibility and reduced restrictions. However, a novel intermittent carbohydrate restricted diet has not been studied chronically, specifically exploring effects adherence and compliance on free living condition and its effect on body composition and food preference. This study primarily aims to explore the acceptability and compliance to ICR, and secondarily aims to explore its effect on behaviour change and body composition in free living condition in health adults. 40 participants (female and male) will follow a single arm novel intermittent carbohydrate diet protocol for 4 weeks. Weight, height, body fat %, waist circumference and resting energy expenditure values will be measured before and after the intervention. Compliance and the effects of dieting on the habitual food intake will be measured using food diaries and 24hr food recalls. Perceptions of participants' towards ICR and their experiences of dieting will be measured using questionnaires and an exit interview. This study will provide vital information for implementing flexible and adaptable dieting strategy, which can provide improvements to physical health in the long-term.
- Conditions
- Healthy
- Being tested
- Intermittent Carbohydrate Restriction (ICR) Protocol
- Keywords
- intermittent carbohydrate restriction, feasibility study, dietary intervention, Behavioural change, Body composition
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Intermittent Carbohydrate Restriction (ICR) ProtocolBehavioural
A novel intermittent carbohydrate restriction (ICR) protocol involving two consecutive low-carbohydrate days (approximately 10% total energy from carbohydrate) followed by five non-restricted days per week, sustained over a 4-week period. Participants receive individualised dietary guidance and support materials to promote adherence in free-living conditions
| Study group | Role | What they receive |
|---|---|---|
| Single-Arm Intermittent Carbohydrate Restriction Intervention | Experimental | Participants in this single-arm feasibility study will follow a structured intermittent carbohydrate restriction (ICR) dietary protocol for four weeks. The ICR approach includes two non-consecutive low-carbohydrate days (≤40g/day) and five habitual eating days per week. The intervention is designed to assess dietary adherence, acceptability, and impact on body composition and food preferences in free-living healthy adults. Data will be collected through anthropometric measurements, dietary assessments (food diaries and 24-hour recalls), and participant-reported outcomes via questionnaires and exit interviews. Receives: Behavioral: Intermittent Carbohydrate Restriction (ICR) Protocol |
What is being measured
The primary outcome is the main question the study is designed to answer.
Adherence to the ICR protocol
Assessed quantitatively as the proportion of participants who successfully follow the prescribed dietary regimen (≥75% of prescribed LC-Ds completed over 4 weeks), measured through 24-hour recalls.
Measured: Throughout the 4-week intervention
Secondary outcomes (11)
Change in body weight (kg)
Measured before and after the 4-week intervention using standard anthropometric techniques.
Measured: Baseline (Week 1) and Week 4 (Final study day)
Changes in resting energy expenditure (kcal/day)
Assessed via indirect calorimetry before and after the intervention. Includes respiratory quotient (RQ) as a metabolic indicator.
Measured: Baseline (Week 1) and Week 4 (Final study day)
Change in daily energy intake (kcal/day)
Assessed via food diaries and 24-hour dietary recalls.
Measured: Baseline (Week 1) and Week 4 (Final study day)
Participant experiences with the ICR intervention (qualitative interview)
Exploratory assessment of participants' behavioral and psychological responses to the ICR intervention, including perceived changes in food preferences and attitudes toward carbohydrate-containing foods . Data will be collected via semi-structured exit interviews and analysed using thematic analysis.
Measured: Week 4 (final study day)
Change in body fat percentage (%)
Measured before and after the 4-week intervention using [method, e.g., bioelectrical impedance
Measured: Baseline (Week 1) and Week 4 (Final study day)
Change in waist circumference (cm)
Measured before and after the 4-week intervention at the midpoint between the iliac crest and lowest rib.
Measured: Baseline (Week 1) and Week 4 (Final study day)
Change in respiratory quotient (VCO₂/VO₂)
Assessed via indirect calorimetry before and after the intervention.
Measured: Baseline (Week 1) and Week 4 (Final study day)
Change in macronutrient distribution (% total energy intake)
Assessed via food diaries and 24-hour dietary recalls.
Measured: Throughout the 4-week intervention
Change in micronutrient distribution (% total energy intake)
Assessed via food diaries and 24-hour dietary recalls.
Measured: Throughout the 4-week intervention
Change in vegetable intake (servings/day)
Assessed via food diaries and 24-hour dietary recalls.
Measured: Throughout the 4-week intervention
Change in oily fish intake (g/week)
Assessed via food diaries and 24-hour dietary recalls.
Measured: Throughout the 4-week intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Jul 2025
- Study start13 Jan 2023
- Primary completion20 Mar 2024
- Study completion20 Apr 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for 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
- Prevention
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- single-arm feasibility study
- Masking
- None (open label)
- Enrolment
- 37 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Surrey
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Kevin Wells, Dr, Study chair, University of Surrey
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07056465
- Sponsor's protocol ID
- FHMS 22-23 054 EGA
- Status last verified
- Jun 2025
- First submitted
- 5 Jun 2025
- Last updated
- 9 Jul 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Biyikoglu H, Robertson MD, Collins AL. Isolating the acute metabolic effects of carbohydrate restriction on postprandial metabolism with or without energy restriction: a crossover study. Eur J Nutr. 2025 Mar 20;64(3):133. doi: 10.1007/s00394-025-03646-5.
PubMed 40111529Biyikoglu H, Tse YT, Ding R, Mold FE, Collins AL. Exploring Adherence and Acceptability of an Intermittent Carbohydrate Restriction Regime (ICARB) in Free-Living Adults: A Feasibility Study. J Hum Nutr Diet. 2026 Feb;39(1):e70188. doi: 10.1111/jhn.70188.
PubMed 41536043
Study at a glance
From the registry record, last updated by the sponsor on 9 Jul 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Acceptability of, and Compliance to a Novel Intermittent Carbohydrate Restriction Dietary Intervention
- ClinicalTrials.gov ID
- NCT07056465
- Acronym / sponsor ID
- FHMS 22-23 054 EGA
- Conditions
- Healthy
- Keywords
- intermittent carbohydrate restriction, feasibility study, dietary intervention, Behavioural change, Body composition
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 37 participants (actual)
- Lead sponsor
- University of SurreyUniversity, hospital or other
- Study start
- 13 Jan 2023 (actual)
- Primary completion
- 20 Mar 2024 (actual)
- Study completion
- 20 Apr 2024 (actual)
- First posted
- 9 Jul 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.
This study investigates a novel dietary approach called Intermittent Carbohydrate Restriction (ICR), which involves reducing carbohydrate intake on selected days of the week while allowing habitual eating on other days. Previous research suggests that intermittent dietary strategies may improve metabolic health and support better adherence compared to continuous calorie restriction.
In this single-arm feasibility study, 40 healthy adults will follow the ICR protocol for 4 weeks. Outcomes including body weight, body fat percentage, waist circumference, and resting metabolic rate will be measured before and after the intervention. Dietary adherence, changes in habitual intake, and participant experiences will be assessed through food diaries, 24-hour recalls, questionnaires, and exit interviews.
The primary aim is to evaluate the acceptability and adherence to the ICR protocol in free-living conditions. Secondary aims include exploring its effects on body composition and diet-related behaviours, with the goal of informing future long-term dietary interventions.
Detailed description
Intermittent energy restriction (IER) has shown to improve postprandial metabolic systems and cognitive function, with superiority in dietary adherence compared with continuous energy restriction (CER)(1-3). A gap in current research is the impact of intermittent carbohydrate restriction (ICR) compared with IER in line with the carbohydrate-insulin model. Novel research (UEC 2019 008 FHMS) has explored the acute effects of ICR on postprandial metabolic systems and found engagement of the same underlying mechanisms with superior outcomes in glucose and lipid metabolism, compared with IER. Unpublished data supports the superiority of ICR over IER in dietary adherence due to perceived increased flexibility and reduced restrictions. However, a novel intermittent carbohydrate restricted diet has not been studied chronically, specifically exploring effects adherence and compliance on free living condition and its effect on body composition and food preference. This study primarily aims to explore the acceptability and compliance to ICR, and secondarily aims to explore its effect on behaviour change and body composition in free living condition in health adults. 40 participants (female and male) will follow a single arm novel intermittent carbohydrate diet protocol for 4 weeks. Weight, height, body fat %, waist circumference and resting energy expenditure values will be measured before and after the intervention. Compliance and the effects of dieting on the habitual food intake will be measured using food diaries and 24hr food recalls. Perceptions of participants' towards ICR and their experiences of dieting will be measured using questionnaires and an exit interview. This study will provide vital information for implementing flexible and adaptable dieting strategy, which can provide improvements to physical health in the long-term.
Study design
- Primary purpose
- Prevention
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- single-arm feasibility study
| Arm | Type | Receives |
|---|---|---|
| Single-Arm Intermittent Carbohydrate Restriction Intervention | Experimental | Behavioral: Intermittent Carbohydrate Restriction (ICR) ProtocolParticipants in this single-arm feasibility study will follow a structured intermittent carbohydrate restriction (ICR) dietary protocol for four weeks. The ICR approach includes two non-consecutive low-carbohydrate days (≤40g/day) and five habitual eating days per week. The intervention is designed to assess dietary adherence, acceptability, and impact on body composition and food preferences in free-living healthy adults. Data will be collected through anthropometric measurements, dietary assessments (food diaries and 24-hour recalls), and participant-reported outcomes via questionnaires and exit interviews. |
Who may qualify
- Ages
- 18 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (7 listed)
- Body Mass Index (BMI) between 18.5 and 29.9 kg/m² (normal to overweight range; avoids confounding from obesity-related metabolic disturbances).
- Generally healthy (self-reported good health with no diagnosed metabolic, cardiovascular, or endocrine disorders).
- Not currently following a weight-loss diet or carbohydrate-restricted diet (to ensure dietary baseline is not already influenced by similar patterns).
- Willing and able to follow the ICR protocol for 4 weeks (includes ability to prepare meals and follow dietary instructions independently).
- Able to attend in-person laboratory assessments at baseline and follow-up (for measurements of REE, body composition, etc.).
Key exclusion criteria (10 listed)
- Diagnosed metabolic or endocrine disorders (e.g., diabetes, hypothyroidism, PCOS), to avoid confounding effects on metabolic outcomes and dietary adherence.
- History of cardiovascular disease, renal disease, or gastrointestinal disorders (e.g., IBS, coeliac disease), which may affect dietary tolerance or nutrient absorption.
- Currently pregnant, breastfeeding, or planning pregnancy during the study (due to potential risks and altered metabolic/nutritional needs).
- BMI <18.5 or ≥30 kg/m² (to exclude underweight or obese individuals where safety and generalizability may differ).
- Currently following a restrictive or structured diet (e.g., ketogenic, low-carb, intermittent fasting, or weight-loss diets), to ensure a clear baseline dietary behavior.
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 |
|---|---|---|
| Intermittent Carbohydrate Restriction (ICR) ProtocolA novel intermittent carbohydrate restriction (ICR) protocol involving two consecutive low-carbohydrate days (approximately 10% total energy from carbohydrate) followed by five non-restricted days per week, sustained over a 4-week period. Participants receive individualised dietary guidance and support materials to promote adherence in free-living conditions | Behavioural | Single-Arm Intermittent Carbohydrate Restriction Intervention |
Primary outcome
Adherence to the ICR protocol
Time frame: Throughout the 4-week intervention
Assessed quantitatively as the proportion of participants who successfully follow the prescribed dietary regimen (≥75% of prescribed LC-Ds completed over 4 weeks), measured through 24-hour recalls.
11 secondary outcomes
Change in body weight (kg)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Changes in resting energy expenditure (kcal/day)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Change in daily energy intake (kcal/day)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Participant experiences with the ICR intervention (qualitative interview)
Time frame: Week 4 (final study day)
Change in body fat percentage (%)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Change in waist circumference (cm)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Change in respiratory quotient (VCO₂/VO₂)
Time frame: Baseline (Week 1) and Week 4 (Final study day)
Change in macronutrient distribution (% total energy intake)
Time frame: Throughout the 4-week intervention
Change in micronutrient distribution (% total energy intake)
Time frame: Throughout the 4-week intervention
Change in vegetable intake (servings/day)
Time frame: Throughout the 4-week intervention
Change in oily fish intake (g/week)
Time frame: Throughout the 4-week intervention
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 9 Jul 2025.
- Background: PubMed 40111529Biyikoglu H, Robertson MD, Collins AL. Isolating the acute metabolic effects of carbohydrate restriction on postprandial metabolism with or without energy restriction: a crossover study. Eur J Nutr. 2025 Mar 20;64(3):133. doi: 10.1007/s00394-025-03646-5.
- Derived from this study: PubMed 41536043Biyikoglu H, Tse YT, Ding R, Mold FE, Collins AL. Exploring Adherence and Acceptability of an Intermittent Carbohydrate Restriction Regime (ICARB) in Free-Living Adults: A Feasibility Study. J Hum Nutr Diet. 2026 Feb;39(1):e70188. doi: 10.1111/jhn.70188.
- 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.
Kevin Wells, Dr study chair
University of Surrey
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Intermittent Carbohydrate Restriction (ICR) Protocol in people with Healthy, run by University of Surrey 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 7 inclusion and 10 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 9 Jul 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 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?
Adherence to the ICR protocol (time frame: Throughout the 4-week intervention). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07056465, which also lists 2 linked publications.
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 2025.