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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
34
Participants will consume each diet for 14 days in a crossover design.
Texas Christian University
Fort Worth, Texas, United States
Endurance Cycling Performance
Time to completion in a 30-kilometer simulated time trial
Time frame: 180 min after the meal begins
Respiratory Exchange Ratio
Indirect calorimetry fasted, postprandial, and during exercise
Time frame: 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
Time frame: Change from baseline at 180 min and 240 min after the meal begins
Oxygen consumption (VO2)
Indirect calorimetry during exercise
Time frame: 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
Time frame: 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
Time frame: 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 \[0-100 mm\]
Time frame: Change from baseline at 60 min, 120 min, 180 min after the meal begins
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Appetite hormones including ghrelin, leptin, insulin, and Peptide-YY
Fasted, postprandial \& post exercise blood concentration of appetite hormones
Time frame: 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
Time frame: 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
Time frame: Change from baseline at 180 min after the meal begins
Cognitive function
Stroop test
Time frame: 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"
Time frame: At 180 min and 240 min after the meal begins
Resting Metabolic Rate
Indirect calorimetry in fasted state
Time frame: At baseline before meal begins
Blood lipids including (triglycerides, total cholesterol, low density lipoprotein, and high-density lipoprotein)
Fasted and postprandial in mg/dL
Time frame: 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