Intermittent Carbohydrate Restriction in Cardiometabolic Health

NCT06684834 | Recruiting

• 1 other identifier: 323721
• Study Type: interventional
• Target: 36
• Locations: 1 country
• Sites: 1

Brief 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. 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.

Conditions

Obesity and Overweight

Keywords

carbohydrate restriction; carbohydrate timing; intermittent carbohydrate restriction; intermittent energy restriction; evening carbohydrate restriction; carbohydrate periodisation

Outcome Measures

Primary Outcomes (1)

• Post Prandial Triglyceride Area Under the Curve (AUC)

  Plasma triglyceride concentrations assessed postprandially for 5 hours after a mixed meal test

  Pre and post intervention (4 weeks)

Secondary Outcomes (12)

• Fat Mass

  Pre and post intervention (4 weeks)

• Lean Body Mass

  Pre and post intervention (4 weeks)

• Fasting and Post Prandial Glucose Concentration

  Pre and post intervention (4 weeks)

• Fasting and Post Prandial Insulin Concentration

  Pre and post intervention (4 weeks)

• Fasting and Post Prandial NEFA Concentration

  Pre and post intervention (4 weeks)

Other Outcomes (9)

• Physical Activity Energy Expenditure (kJ or kcal)

  1 week during baseline monitoring, and weeks 1 and 4 of the intervention

• Time Spent in Different Physical Activity Intensities (minutes)

  1 week during baseline monitoring, and weeks 1 and 4 of the intervention

• Dietary Intake

  1 week during baseline monitoring, and weeks 1 and 4 of intervention

Study Arms (3)

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.

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.

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.

Interventions

5:2 carbohydrate restriction OTHER

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.

5:2 carbohydrate restriction (5:2CR)

Early time-restricted carbohydrate intake OTHER

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.

Early time-restricted carbohydrate intake (eTRC)

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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)

You may not qualify if:

• 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
• 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

Sponsors & Collaborators

• University of Bath: lead

Study Sites (1)

University of Bath

Bath, Somerset, BA2 7AY, United Kingdom

RECRUITING

MeSH Terms

Conditions

Obesity; Overweight

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Guoda Karoblyte

CONTACT

+44 (0) 1225 386478; gk678@bath.ac.uk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Model Details: A randomised, three-arm parallel-group study

Study Record Dates

• First Submitted: October 24, 2024
• First Posted: November 12, 2024
• Study Start: September 5, 2023
• Primary Completion: October 1, 2025
• Study Completion (Estimated): October 1, 2036
• Last Updated: November 12, 2024

Record last verified: 2024-11

Locations

GB (1)