Effect of Glycemic Index on Physical Capacity in Runners

Study Overview
=================
Brief Summary
-----------------
The purpose of the present study was to assess the influence of low vs moderate glycemic index of a 3-week diet on aerobic capacity, endurance performance and body mass and composition in endurance-trained athletes in a randomized, controlled crossover trial.

Detailed Description
-----------------
The effect of glycemic index of pre-exercise meal on endurance capacity and performance has been widely investigated. However, little is known about the adaptations to longer dietary interventions with different glycemic index and their influence on aerobic capacity and body composition in runners. Therefore, the purpose of this study was the assessment of the influence of low GI vs moderate GI of a 3-week diet on aerobic capacity, endurance performance and body mass and composition in endurance-trained athletes in a randomised, controlled crossover trial.

Official Title
-----------------
Effects of Low and Versus Moderate Glycemic Index Diets on Physical Capacity and Body Composition in Endurance- Trained Runners

Conditions
-----------------
Nutrition, Sport, Glycemic Index, Physical Capacity

Intervention / Treatment
-----------------
* Other: Dietary Intervention: Low vs. moderate glycemic index


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: written consent to participate, male and female, a current medical clearance to practice sports, training experience: at least 3 years, minimum of 4 workout sessions a week lasting at least 1.5-2 hours/day, age: 17 - 37 years. Exclusion Criteria: current injury, any health-related contraindication, declared general feeling of being unwell, unwilling to follow the study protocol, smoking, illicit drug use, alcohol consumption greater than 1-2 drinks/week, dietary supplements use less than 3 weeks before the study, females- being pregnant or planning to become pregnant during the study.

Ages Eligible for Study
-----------------
Minimum Age: 17 Years
Maximum Age: 37 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Low Glycemic Index Diet<br>Group consuming low glycemic index diet. Calculated glycemic index of daily diet was lower than 40. Carbohydrate- containing foods included whole rye bread, pumpernickel bread, whole oats, wheat brans, brown rice, buckwheat, vegetables (besides corn, cooked carrots, potatoes and pumpkin) and fruit such as apples, pears, grapefruits, tangerines, prunes, dried apricots and unripe bananas. Interventions: The experimental procedure for each participant included a 3-week low glycemic index diet. Between the 3-week low and moderate glycemic index diets or a moderate and low glycemic index treatment, a 14-day washout period was introduced. | Other: Dietary Intervention: Low vs. moderate glycemic index<br> <br> |
| Experimental: Moderate Glycemic Index Diet<br>Group consuming moderate glycemic index diet. Calculated glycemic index of diet was higher than 60. Carbohydrate- containing foods included wheat bread, wheat rolls, potatoes, instant oats, cornflakes, white rice, millet, boiled carrots and fruit (ripe bananas, grapes, raisins, dates, cranberry, honey and high sugar jams) Interventions: The experimental procedure for each participant included a 3-week moderate glycemic index diet. Between the 3-week low and moderate glycemic index diets or a moderate and low glycemic index treatment, a 14-day washout period was introduced. | Other: Dietary Intervention: Low vs. moderate glycemic index<br> <br> |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in aerobic capacity following low glycemic index diet |  | Baseline and after 3 weeks | 
| Changes in aerobic capacity following moderate glycemic index diet |  | Baseline and after 3 weeks | 
| Changes in performance in 12-min running test following low glycemic index diet |  | Baseline and after 3 weeks | 
| Changes in performance in 12-min running test following moderate glycemic index diet |  | Baseline and after 3 weeks | 
| Changes in fat mass and fat free mass following low glycemic index diet | Fat mass (kg) and fat free mass (kg) analysis | Baseline and after 3 weeks | 
| Changes in fat mass and fat free mass following moderate glycemic index diet | Fat mass (kg) and fat free mass (kg) analysis | Baseline and after 3 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Statistical evaluation of the significance of differences between the changes in aerobic capacity indices |  | 1 year | 
| Statistical evaluation of the significance of differences between the changes in performance in 12-min running test |  | 1 year | 
| Statistical evaluation of the significance of differences between the changes in fat mass and fat free mass | Fat mass (kg) and fat free mass (kg) | 1 year | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Nutrition, Training support, Low Glycemic Index, Moderate Glycemic Index, Endurance, Running