The Effects of 24-hour Fasting or Carbohydrate Restriction on Postprandial Metabolic Responses

NCT ID: NCT07250191

Last Updated: 2025-11-26

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 16 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2023-10-16
• Study Completion Date: 2025-11-06

Brief Summary

Most individuals spend the majority of the day in a fed state, making postprandial blood glucose and lipid regulation a central component of metabolic health. Short periods of fasting or reduced carbohydrate intake can occur frequently in daily life, whether through intentional dietary practices (e.g. intermittent fasting), cultural or religious traditions, or unstructured eating patterns. These periods can induce measurable metabolic changes, but the acute effects of a single 24-hour period of fasting or carbohydrate restriction on postprandial metabolism upon refeeding remain poorly characterised.

This study will examine how 24 hours of either complete fasting or low carbohydrate intake without energy restriction influence postprandial blood glucose and lipid concentrations, as well as related metabolic markers, in healthy adults, in comparison to a habitual high carbohydrate control diet. Participants will complete all three conditions in a randomised order, consuming a standardised meal test after each 24-hour condition. Repeated blood sampling and gas exchange measurements will be carried out to assess postprandial metabolic responses.

The aim of this study is to characterise whether acute periods of fasting and low carbohydrate restriction elicit distinct or comparable alterations in postprandial metabolic responses. A clearer understanding of these acute physiological effects can help inform how variations in eating patterns influence glucose and lipid handling in individuals without metabolic disease.

Conditions

Glucose and Lipid Metabolism

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Habital control diet

100% of energy requirements, ≥150 carbohydrate/day

Group Type: NO_INTERVENTION

No interventions assigned to this group

Fasting

No energy intake

Group Type: EXPERIMENTAL

Fasting

Intervention Type: BEHAVIORAL

No food intake for 24 hours

Carbohydrate Restriction

100% of energy requirements, ≤20g carbohydrate

Group Type: EXPERIMENTAL

Carbohydrate restriction

Intervention Type: BEHAVIORAL

Restriction of dietary carbohydrate to ≤5% of total energy intake for 24 hours

Interventions

Fasting

No food intake for 24 hours

Intervention Type: BEHAVIORAL

Carbohydrate restriction

Restriction of dietary carbohydrate to ≤5% of total energy intake for 24 hours

Intervention Type: BEHAVIORAL

Other Intervention Names

Ketogenic diet

Eligibility Criteria

Inclusion Criteria

• Aged between 18-40 years
• Have a BMI of 18.5-29.9 kg/m2

Exclusion Criteria

1. Diagnosed with any major chronic conditions (e.g. type 2 diabetes, coronary heart disease, cancer, chronic kidney disease, etc.)

2. Use of medication that may interfere with study outcomes (e.g. glucose or lipid-lowering medications)

3. Currently or recently pregnant (within last 6 months), planning to get pregnant or currently lactating

4. Has a habitually low carbohydrate intake (<150g carbohydrates/day)

5. Current or previous eating disorder

6. Has donated more than 500ml of blood in the last 3 months prior to the initial laboratory visit

7. Insufficient mental capacity or language skills to independently understand and follow the study protocol

8. Has an irregular sleeping pattern (e.g. due to undertaking night-shift work)

9. Any other condition, concurrent intervention or behaviour deemed either to pose undue personal risk to the participant or to introduce bias into the experiment

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 40 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Bath

OTHER

Sponsor Role: lead

Responsible Party

Guoda Karoblyte

Doctoral Researcher

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

University of Bath

Bath, , United Kingdom

Countries

United Kingdom

Other Identifiers

0590

Identifier Type: -

Identifier Source: org_study_id