Glycaemic Index and Substrate Metabolism (GI)

Influence of a Diet With Different Glycaemic Indices and Carbohydrate Content on Substrate Utilization, Energy Storage, and Performance-related Parameters in Endurance-trained Men

Substrate metabolism during exercise can be influenced by various nutritional regimes. The effectiveness of the different nutritional regimes, which differ in their carbohydrate content, will be investigated not only by functional tests but also the measurement of the mechanistic processes in the muscle will be explored.

Magnetic resonance (MR), better known as magnetic resonance imaging (MRI), has been widely used in clinical practice as a non-invasive imaging technique. Importantly, in addition to producing anatomical images, an MR scanner also offers the possibility to measure the concentrations of a number of metabolic products. This is done through a technique known as magnetic resonance spectroscopy (MRS).

This research project asks the following questions:

• Can a diet containing carbohydrates with a low glycemic index achieve the same adaptations in basic endurance/fat metabolism as a high fat, low carbohydrate (ketogenic) diet?
• Does a high-fat, low-carbohydrate diet, compared with a high-carbohydrate diet, prevent improvements in performance in the submaximal and maximal range?
• What is the effect of diets with different carbohydrate content and variable glycemic index on endurance performance in a half marathon and a time trial?
• How do the diets with different carbohydrate content and variable glycaemic index affect the energy and glycogen stores in the muscles?

In active recreational athletes, the objectives are: (1) to investigate the effects of different diets with variable carbohydrate content and glycaemic index on substrate metabolism, (2) to determine the effects of the different diets on energy stores using multinuclear dynamic magnetic resonance spectroscopy, and (3) to measure the effects of the different diets on endurance performance.

Study Overview

• Status: Completed
• Conditions: Substrate Metabolism During Exercise
• Intervention / Treatment: Other: Training intervention; Other: Low Glycaemic Index; Other: High Glycaemic Index; Other: LCHF

• Study Type: Interventional
• Enrollment (Actual): 65
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Austria
  • Vienna, Austria, 1070
    • University of Vienna

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Male gender
• Age between 18 and 40 years
• Recreational active in leisure time (2-3x/week physical activity)
• Motivation for performance testing and structured training plan
• Interest in different diets
• no acute or chronic illnesses

Exclusion Criteria:

• Contraindications to physical exercise according to ACSM (American College of Sports Medicine) guidelines
• Age <18 or >40 years
• Taking medication that could influence the measurements or that is prohibited in training and/or competition according to the WADA (World Anti-Doping Agency) Code
• Competitive athlete with own training plan
• Experience with intervention diets

MRI-specific exclusion criteria:

• Claustrophobia
• Cardiac pacemaker
• cochlear implant
• subcutaneous injection system
• Stents, metal implants, braces, piercings, tattoos
• Body weight of more than 180 kg or BMI of more than 37 kg/m2

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low GI; The subjects eat 55-60 E-% carbohydrates with ≥ 65 % from low glycaemic index carbohydrates per day, the other E-% are fats and proteins.	Other: Training intervention; The training intervention will be a 10 week training plan for endurance runners. The plan consists of five sessions per week (three basic endurance sessions and two interval sessions); Other: Low Glycaemic Index; The subjects eat 55-60 E-% carbohydrates with ≥ 65 % from low glycaemic index carbohydrates per day, the other E-% are fats and proteins.
Active Comparator: High GI; The subjects eat 55-60 E-% carbohydrates with ≥ 65 % from high glycaemic index carbohydrates per day, the other E-% are fats and proteins.	Other: Training intervention; The training intervention will be a 10 week training plan for endurance runners. The plan consists of five sessions per week (three basic endurance sessions and two interval sessions); Other: High Glycaemic Index; The subjects eat 55-60 E-% carbohydrates with ≥ 65 % from high glycaemic index carbohydrates per day, the other E-% are fats and proteins.
Experimental: Low Carb High Fat; The subjects eat ≥ 65 E-% fats and a maximum of 50 g carbohydrates per day.	Other: Training intervention; The training intervention will be a 10 week training plan for endurance runners. The plan consists of five sessions per week (three basic endurance sessions and two interval sessions); Other: LCHF; The subjects eat ≥ 65 E-% fats and a maximum of 50 g carbohydrates per day.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
changes in peak oxygen consumption (measured in ml/min/kg)	VO2peak will be assessed during a graded exercise test on the treadmill.	Baseline - 10 weeks
changes in 5 km time trial (measured in mm:ss)	5 km time trial performance will be assessed during an all out 5 km run on a 400 m running track. The time for completing the 5 km will be assessed.	Baseline - 10 weeks
changes in muscle glycogen content (measured in mmol/l muscle)	Changes in muscle glycogen will be assessed in a thigh muscle using a MR scan.	Baseline - 10 weeks
changes in power at lactate turning point 1 (LTP1) and individual anaerobic threshold (IAS) (measured in km/h)	Changes in power at LTP1 and IAS will be assessed during a graded exercise test on a treadmill.	Baseline - 10 weeks
changes in AUC in lactate in the graded exercise test	Changes in AUS in lactate will be assessed during a graded exercise test on a treadmill.	Baseline - 10 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
changes in fat free mass (measured in kg)	Changes in fat free mass will be assessed using a bioelectrical impedance analysis.	Baseline - 5 weeks - 10 weeks
changes in fat mass (measured in kg)	Changes in fat mass will be assessed using a bioelectrical impedance analysis.	Baseline - 5 weeks - 10 weeks
changes in skeletal muscle mass (measured in kg)	Changes in skeletal muscle mass will be assessed using a bioelectrical impedance analysis.	Baseline - 5 weeks - 10 weeks
changes in body water (measured in l)	Changes in total and extracellular body water will be assessed using a bioelectrical impedance analysis.	Baseline - 5 weeks - 10 weeks
changes in body weight (measured in kg)	Changes in body weight will be assessed using a bioelectrical impedance analysis.	Baseline - 5 weeks - 10 weeks
changes in body mass index	Changes in body mass index will be assessed using a bioelectrical impedance analysis. The weight and the height will be used to calculate changes in BMI in kg/m^2.	Baseline - 5 weeks - 10 weeks
completion time of a half marathon performance (measured in hh:mm:ss)	The half marathon performance will be assessed during an official marathon race. The time of completion of the half marathon will be assessed.	after 10 weeks
changes in cholesterin and cholesterin subunits (measured in mg/dl)	Changes in cholesterin and cholesterin subunits (LDL and HDL cholesterin) will be assessed with a routine blood count.	Baseline - 10 weeks
changes in rated perceived exhaustion (RPE) in 5 km time trial	The changes in RPE will be assessed during the 5 km time trial on a running track. The RPE scale ranges from 6 to 20, where 20 means "really, really exhausting".	Baseline - 10 weeks

Collaborators and Investigators

• Sponsor: University of Vienna
• Collaborators: Medical University of Vienna

Study record dates

Study Major Dates

• Study Start (Actual): January 10, 2022
• Primary Completion (Actual): April 23, 2023
• Study Completion (Actual): April 23, 2023

Study Registration Dates

• First Submitted: January 25, 2022
• First Submitted That Met QC Criteria: February 4, 2022
• First Posted (Actual): February 16, 2022

Study Record Updates

• Last Update Posted (Actual): November 27, 2023
• Last Update Submitted That Met QC Criteria: November 21, 2023
• Last Verified: November 1, 2023

More Information

Terms related to this study

• Other Study ID Numbers: 2105/2021

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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