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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| High Carbohydrate Diet | Experimental | Participants will consume a high carbohydrate diet (65-75% of total energy intake). Protein intake will be standardized at 15% of total energy intake. |
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| Ketogenic Diet | Experimental | Participants will consume a low carbohydrate diet (<5-10% of total energy intake). Protein intake will be standardized at 15% of total energy intake. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Diet | Other | Participants will consume each diet for 14 days in a crossover design. |
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| Measure | Description | Time Frame |
|---|---|---|
| Endurance Cycling Performance | Time to completion in a 30-kilometer simulated time trial | 180 min after the meal begins |
| 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 |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Texas Christian University | Fort Worth | Texas | 76129 | United States |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 38229197 | Derived | Graybeal AJ, Kreutzer A, Moss K, Shah M. Changes in the chronic and postprandial blood lipid profiles of trained competitive cyclists and triathletes following a ketogenic diet: a randomized crossover trial. BMC Sports Sci Med Rehabil. 2024 Jan 16;16(1):19. doi: 10.1186/s13102-023-00801-5. |
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De-identified study data of all outcome variables will be shared on an Open Science Framework project page (osf.io) along with the study protocol, statistical analysis plan, and analytic code
Will become available at the latest June 2021 and be available indefinitely
Openly available
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| ID | Term |
|---|---|
| D004032 | Diet |
| ID | Term |
|---|---|
| D009747 | Nutritional Physiological Phenomena |
| D000066888 | Diet, Food, and Nutrition |
| D010829 | Physiological Phenomena |
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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 |