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

NCT ID: NCT07056465

Last Updated: 2025-07-09

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 37 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2023-01-13
• Study Completion Date: 2024-04-20

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.

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 Unpublished data supports the superiority of ICR over IER in dietary adherence due to perceived increased flexibility and reduced restrictions.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

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: PREVENTION
• Blinding Strategy: NONE

Study Groups

Single-Arm Intermittent Carbohydrate Restriction Intervention

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.

Group Type: EXPERIMENTAL

Intermittent Carbohydrate Restriction (ICR) Protocol

Intervention Type: 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

Interventions

Intermittent Carbohydrate Restriction (ICR) Protocol

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

Intervention Type: BEHAVIORAL

Eligibility Criteria

Inclusion Criteria

• 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).

Exclusion Criteria

• 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).

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 60 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Surrey

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Kevin Wells, Dr

Role: STUDY_CHAIR

University of Surrey

Locations

University of Surrey

Guildford, Surrey, United Kingdom

Countries

United Kingdom

References

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.

Reference Type: BACKGROUND

PMID: 40111529 (View on PubMed)

Other Identifiers

FHMS 22-23 054 EGA

Identifier Type: -

Identifier Source: org_study_id