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

NCT07250191 | Completed

• 1 other identifier: 0590
• Study Type: interventional
• Target: 16
• Locations: 1 country
• Sites: 1

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

Keywords

carbohydrate restriction; fasting; intermittent energy restriction

Outcome Measures

Primary Outcomes (2)

• Triglyceride Concentration

  Plasma triglyceride concentrations assessed at baseline and postprandially for 2 hours after a mixed meal test

  After each 24-hour dietary condition

• Glucose Concentration

  Plasma glucose concentrations assessed at baseline and postprandially for 2 hours after a mixed meal test

  After each 24-hour dietary condition

Secondary Outcomes (4)

• Insulin Concentration

  After each 24-hour dietary condition

• Non-esterified Fatty Acid Concentration

  After each 24-hour dietary condition

• Beta-hydroxybutyrate Concentration

  After each 24-hour dietary condition

• Substrate Oxidation

  After each 24-hour dietary condition

Study Arms (3)

Habital control diet

NO INTERVENTION

100% of energy requirements, ≥150 carbohydrate/day

Fasting

EXPERIMENTAL

No energy intake

Behavioral: Fasting

Carbohydrate Restriction

EXPERIMENTAL

100% of energy requirements, ≤20g carbohydrate

Behavioral: Carbohydrate restriction

Interventions

Fasting BEHAVIORAL

No food intake for 24 hours

Fasting

Carbohydrate restriction BEHAVIORAL

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

Also known as: Ketogenic diet

Carbohydrate Restriction

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

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

You may not qualify if:

• Diagnosed with any 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 a habitually low carbohydrate intake (\<150g carbohydrates/day)
• Current or previous eating disorder
• 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
• Has an irregular sleeping pattern (e.g. due to undertaking night-shift work)
• Any other 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, BA2 7AY, United Kingdom

Location

MeSH Terms

Conditions

Fasting

Interventions

Angptl4 protein, mouse; Diet, Ketogenic

Condition Hierarchy (Ancestors)

Feeding Behavior; Behavior

Intervention Hierarchy (Ancestors)

Diet, Carbohydrate-Restricted; Diet Therapy; Nutrition Therapy; Therapeutics; Diet; Nutritional Physiological Phenomena; Diet, Food, and Nutrition; Physiological Phenomena

Study Design

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

Study Record Dates

• First Submitted: November 18, 2025
• First Posted: November 26, 2025
• Study Start: October 16, 2023
• Primary Completion: January 20, 2024
• Study Completion: November 6, 2025
• Last Updated: November 26, 2025

Record last verified: 2025-11

Data Sharing

• IPD Sharing: Will not share

Locations

GB (1)