The Effects of Combined Energy and Carbohydrate Restriction on Exercise Capacity (CHO-EX)

The Effects of Combined Energy and Carbohydrate Restriction on Exercise Capacity and Health in Overweight Women

The effect of calorie restriction combined with low or moderate carbohydrate availability on exercise capacity, metabolism and metabolic health indicators will be measured in a randomized parallel group design. Forty overweight (BMI 25-30) and relatively inactive women (20-35 of age) will be included. These will be randomized into one of two experimental groups both receiving a calorie-restricted diet (-1000 kcal) combined with either low carbohydrate availability or moderate carbohydrate availability across a 10 day period. Laboratory-based physical capacity tests and blood and muscle sampling will be performed before and after the intervention. In addition, an additional follow-up test day will be performed after continuing the diet for another 48 h and then standardizing the pre-testing carbohydrate availability before repeating the tests of physical capacity.

Study Overview

• Status: Completed
• Conditions: Overweight and Obesity
• Intervention / Treatment: Other: Calorie-restriction with low carbohydrate; Other: Calorie-restriction with moderate carbohydrate

Detailed Description

Overweight (BMI 25-30), but healthy premenopausal women aged 20-35 years (n=40) will be included in the trial, which is structured as a randomized, parallel group design where participants are randomized to either consume a hypocaloric diet (-1000 kcal) with concurrent carbohydrate restriction (low carbohydrate, L-CHO, n=20) or a similar hypocaloric diet with moderate carbohydrate availability (moderate carbohydrate, M-CHO, n=20). The trial will be single-blinded since it might be transparent to the participants which diet they are consuming, whereas the test personnel collecting and processing test results will be blinded to diet allocation. Diet handling will be managed by specific individuals in the research group who do not partake in executing the physical capacity tests. Additionally, the direction of the trial's primary hypothesis will not be disclosed to the participants to avoid creating preconceived expectations about the effects.

After an initial screening interview and two familiarization visits, participants will complete the intervention period consisting of 10 days with the allocated diet manipulation with preceding and subsequent test days with a series of tests. The tests before and after each test period include measurements of the participants' physical capacity level and energy metabolism in the laboratory as well as blood and muscle sampling. In addition, resting metabolism and body composition will be measured. During each test period, participants' habitual activity level will be monitored with an accelerometer attached to the wrist (Axivity). There will also be monitoring of the activity level with an accelerometer in a 7-day cycle before the start of the trial as a baseline measurement.

Similarly, a glucose monitor will be placed on the upper arm for continuous glucose readings via a Freestyle Libre2 sensor during the trial period.

• Study Type: Interventional
• Enrollment (Actual): 36
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Denmark
  • Aarhus C, Denmark, 8000
    • Section for Sport Science, Department of Public Health, Aarhus University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age: 20-35
• BMI: 25-30

Exclusion Criteria:

• Irregular menstruation within the last 6 months (shorter end 24 days or longer end 35 days cycle)
• Injuries / pain in the lower body, which prevents participation in intense cycling
• Medication consumption that may affect primary outcome measures.
• Smoking
• Pregnancy
• Systematic physical activity more than 2 hours per week

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Low-carbohydrate calorie-restriction; Minimum of 3 g carbohydrate/kg body weight/day and a ~1000 kcal calorie restriction	Other: Calorie-restriction with low carbohydrate; Calorie-restriction and low carbohydrate availability
Experimental: Moderate-carbohydrate calorie-restriction; Maximum of 1 g carbohydrate/kg body weight/day and a ~1000 kcal calorie restriction	Other: Calorie-restriction with moderate carbohydrate; Calorie-restriction and moderate carbohydrate availability

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time to exhaustion	Time to exhaustion at 85% VO2max	Pre, post (day 11 of the intervention) and follow-up (day 2 after the post measurement)
Sprint performance	Peak and mean 15-s sprint performance	Pre, post (day 11 of the intervention) and follow-up (day 2 after the post measurement)
Exercise tolerance	Ratings of perceived exertion (Borg scale) during standardized-intensity exercise from 6 (lowest exertion) to 20 (highest exertion)	Pre, post (day 11 of the intervention) and follow-up (day 2 after the post measurement)
Muscle glycogen levels	Muscle glycogen levels obtained from biopsy sample	Pre and post (day 11 of the intervention)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Physical activity level	Measured with accelerometer during the intervention	During the intervention (days 1 to 11 of the intervention)
Maximal fat oxidation capacity	Maximal fat oxidation measured in the laboratory	Pre, post (day 11 of the intervention) and follow-up (day 2 after the post measurement)
Muscle metabolic enzyme activity	Activity of key enzymes involved in carbohydrate and fat metabolism	Pre and post (day 11 of the intervention)
Blood lipid profile	High-density lipoproteins, low-density lipoproteins, very-low-density lipoproteins, cholesterol, free fatty acids and triglycerides	Pre and post (day 11 of the intervention)
Continuous glucose levels	Glucose levels measured continuously across the trial + during exercise tests	14 days from the day before the intervention, throughout the intervention (days 1 to 11) and 2 days after the intervention (follow-up)
Fasting blood glucose and insulin	Insulin sensitivity (Homa 2 IR)	Pre and post (day 11 of the intervention)
Long-term glycemic control (HbAc1)	Measured from fasting blood	Pre and post (day 11 of the intervention)

Collaborators and Investigators

• Sponsor: University of Aarhus
• Collaborators: University of Southern Denmark; University Ghent

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2024
• Primary Completion (Actual): June 15, 2025
• Study Completion (Actual): July 1, 2025

Study Registration Dates

• First Submitted: April 5, 2024
• First Submitted That Met QC Criteria: April 19, 2024
• First Posted (Actual): April 24, 2024

Study Record Updates

• Last Update Posted (Actual): March 2, 2026
• Last Update Submitted That Met QC Criteria: February 27, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Physical activity; Diet; Carbohydrate; Metabolism; Physical capacity; Macronutrients
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Pathological Conditions, Signs and Symptoms; Behavior; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Motor Activity
• Other Study ID Numbers: 1-10-72-19-24

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No