The Effect of Diet Composition on Performance, Expenditure, Blood Lipids, and Appetite Hormones in Highly Trained Cyclists

Study Overview
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Brief Summary
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This study employs a crossover design to evaluate the effect of two different diets (high carbohydrate vs. ketogenic) and corresponding test meals on endurance exercise performance, energy expenditure including resting metabolic rate and thermic effect of food, postprandial responses of blood lipids, glucose and appetite hormones, and cognitive function and mood states.

Detailed Description
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Traditionally, a high carbohydrate diet is recommended for elite endurance athletes and sub-elite, highly trained recreational athletes competing in endurance events. However, recently the ketogenic diet (extremely low carbohydrate content) has become popular in these populations. The effect on endurance exercise performance, energy expenditure, postprandial blood profiles, and cognitive function and mood states requires further investigation. In this study, highly trained recreational cyclists and triathletes will adhere to each diet (high-carbohydrate and ketogenic) for 14 days in a crossover design. Experimental trials at baseline and after each diet will evaluate endurance cycling performance (time trial), resting energy expenditure, the thermic effect of food of test meals corresponding in composition to each diet, postprandial responses of blood lipids, glucose and appetite hormones, and cognitive function and mood states.

Official Title
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The Effect of Diet Composition on Performance, Energy Expenditure, Blood Lipids and Lipoproteins, and Cognitive Function and Mood States in Highly Trained Cyclists

Conditions
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Endurance Cycling Performance

Intervention / Treatment
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* Other: Diet


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: >100-150km of cycling per week VO2max > 80th percentile for sex and age (adjusted for cycle ergometry) apparently healthy Exclusion Criteria: weight loss supplements/medications/diet extreme dietary patterns (e.g. extremely high or low carbohydrate) nicotine use heavy alcohol use (>7 drinks/week female; >14 drinks/week male) food allergies diabetes heart disease stroke liver/kidney/thyroid disease anemia eating disorders uncontrolled hypertension pulmonary/orthopedic/musculoskeletal problems that prevent exercise surgery that affects swallowing and digestion claustrophobia

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High Carbohydrate Diet<br>Participants will consume a high carbohydrate diet (65-75% of total energy intake). Protein intake will be standardized at 15% of total energy intake. | Other: Diet<br>* Participants will consume each diet for 14 days in a crossover design.<br>|
| Experimental: Ketogenic Diet<br>Participants will consume a low carbohydrate diet (<5-10% of total energy intake). Protein intake will be standardized at 15% of total energy intake. | Other: Diet<br>* Participants will consume each diet for 14 days in a crossover design.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Endurance Cycling Performance | Time to completion in a 30-kilometer simulated time trial | 180 min after the meal begins | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory Exchange Ratio | Indirect calorimetry fasted, postprandial, and during exercise | Change from baseline at 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, 192 min, 204 min, 216 min, 228 min and 240 min after the meal begins | 
| Muscle Fuel Rating | Ultrasound echogenicity of Rectus Femoris | Change from baseline at 180 min and 240 min after the meal begins | 
| Oxygen consumption (VO2) | Indirect calorimetry during exercise | At 192 min, 204 min, 216 min, 228 min and 240 min after the meal begins | 
| Rating of Perceived Exertion (RPE) | 6-20 Borg's scale during exercise | At 192 min, 204 min, 216 min, 228 min and 240 min after the meal begins | 
| Thermic Effect of Food (postprandial energy expenditure) | Fasted vs. postprandial indirect calorimetry | Change from baseline at 30 min, 60 min, 90 min, 120 min, 150 min, 180 min after the meal begins | 
| Subjective appetite ratings | Visual Analog Scale (Scale 1: Perception of Hunger [0-100 mm]; Scale 2: Perception of Fullness [0-100 mm]; Scale 3: Desire to Eat [0-100 mm] | Change from baseline at 60 min, 120 min, 180 min after the meal begins | 
| Appetite hormones including ghrelin, leptin, insulin, and Peptide-YY | Fasted, postprandial & post exercise blood concentration of appetite hormones | Change from baseline at 30 min, 60 min, 120 min, 180 min and 240 min | 
| Blood glucose | Fasted, postprandial & post exercise blood concentration of glucose | Change from baseline at 180 min and 240 min after the meal begins; on day 7 of each diet | 
| Blood pressure | Fasted, postprandial & post exercise | Change from baseline at 180 min after the meal begins | 
| Cognitive function | Stroop test | At 180 min and 240 min after the meal begins | 
| Mood state questionnaire | Abbreviated Profile of Mood States; 40-item scale; Likert scale from 0 = not at all to 4 = extremely | At 180 min and 240 min after the meal begins | 
| Resting Metabolic Rate | Indirect calorimetry in fasted state | At baseline before meal begins | 
| Blood lipids including (triglycerides, total cholesterol, low density lipoprotein, and high-density lipoprotein) | Fasted and postprandial in mg/dL | Change from baseline at 30 min, 60 min, 120 min, 180 min, 192 min, 204 min, 216 min, 228 min and 240 min after the meal begins |