Exploring Adherence and Acceptability of an Intermittent Carbohydrate Restriction Regime in Free-Living Adults: A Feasibility Study

NCT07056465 | Completed

• 1 other identifier: FHMS 22-23 054 EGA
• Study Type: interventional
• Target: 37
• Locations: 1 country
• Sites: 1

Brief 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. 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.

Conditions

Healthy

Keywords

intermittent carbohydrate restriction; feasibility study; dietary intervention; Behavioural change; Body composition

Outcome Measures

Primary Outcomes (1)

• 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.

  Throughout the 4-week intervention

Secondary Outcomes (11)

• Change in body weight (kg)

  Baseline (Week 1) and Week 4 (Final study day)

• Changes in resting energy expenditure (kcal/day)

  Baseline (Week 1) and Week 4 (Final study day)

• Change in daily energy intake (kcal/day)

  Baseline (Week 1) and Week 4 (Final study day)

• Participant experiences with the ICR intervention (qualitative interview)

  Week 4 (final study day)

• Change in body fat percentage (%)

  Baseline (Week 1) and Week 4 (Final study day)

Study Arms (1)

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.

Behavioral: Intermittent Carbohydrate Restriction (ICR) Protocol

Interventions

Intermittent Carbohydrate Restriction (ICR) Protocol BEHAVIORAL

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

Single-Arm Intermittent Carbohydrate Restriction Intervention

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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).

You may not qualify if:

• 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.
• 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).

Sponsors & Collaborators

• University of Surrey: lead

Study Sites (1)

University of Surrey

Guildford, Surrey, GU2 7XH, United Kingdom

Location

Related Publications (2)

• 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.

  PMID: 40111529 BACKGROUND

• Biyikoglu 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.

  PMID: 41536043 DERIVED

MeSH Terms

Interventions

Clinical Protocols

Intervention Hierarchy (Ancestors)

Therapeutics; Epidemiologic Study Characteristics; Health Care Evaluation Mechanisms; Quality of Health Care; Health Care Quality, Access, and Evaluation

Study Officials

• Kevin Wells, Dr

  University of Surrey

  STUDY CHAIR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: PREVENTION
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: single-arm feasibility study

Study Record Dates

• First Submitted: June 5, 2025
• First Posted: July 9, 2025
• Study Start: January 13, 2023
• Primary Completion: March 20, 2024
• Study Completion: April 20, 2024
• Last Updated: July 9, 2025

Record last verified: 2025-06

Data Sharing

• IPD Sharing: Will not share

Locations

GB (1)