FueL Use During eXercise in Males and Females
ConditionHealthy Adults
Trial statusRecruiting
Trial phaseNot applicable
Trial typeInterventional
Biological sexAll
Age18-35
SponsorUniversity of Toronto
About this trial
This study will investigate whether pre-exercise nutrition influences sex differences in fuel utilization during endurance exercise. Twenty-four recreationally active adults (12 females and 12 males) will complete three experimental exercise trials in a randomized, counterbalanced crossover design. Before each trial, participants will consume either a carbohydrate beverage, a protein-based beverage, or a flavour-matched non-caloric beverage representing the fasted condition. Thirty minutes later, participants will complete 90 minutes of moderate-intensity cycling followed by a cycling time-to-task-failure test. Whole-body carbohydrate and fat oxidation, exogenous substrate oxidation, blood metabolites, and exercise performance will be assessed.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Participating in ≥150 minutes of moderate-to-vigorous physical activity per week
VO₂peak classified as "good" or above based on American College of Sports Medicine normative values: >35.0 mL/kg/min for females and >39.0 mL/kg/min for males
Body mass index (BMI) between 18 and 27 kg/m²
Participating in 3-5 structured exercise sessions per week
Disqualifiers
Polycystic ovarian syndrome (PCOS) or endometriosis Current use of oral contraceptives or oral contraceptive use within the previous 3 months Diagnosed cardiovascular or metabolic disease Hypergonadism or hypogonadism Use of medications for management of blood glucose or lipid metabolism Pregnant or <12 months postpartum Lactating or breastfeeding within 3 months of study commencement Menopausal Recreational tobacco smoking Inability to complete the study exercise protocols or comply with pre-trial dietary or physical activity controls Use of medications that may affect substrate metabolism, including corticosteroids or non-steroidal anti-inflammatory drugs (NSAIDs) Currently following a low-carbohydrate diet, such as a ketogenic or Atkins diet
Trial design
Design model
Crossover
Treatments tested in this trial
Pre-exercise carbohydrate beverage
Dietary supplementA carbohydrate beverage providing 1 g glucose/kg body mass, enriched with 1 mg/kg body mass \[U-13C6\]-D-glucose for assessment of exogenous carbohydrate oxidation, with calorie-free flavouring. The beverage will be consumed within 5 minutes, 30 minutes before exercise.
Pre-exercise protein beverage
Dietary supplementA protein-based beverage providing 0.45 g protein/kg body mass and supplemented with 0.24 g fat/kg body mass to match the energy content of the carbohydrate condition. The beverage is enriched with L-\[1-13C\]leucine and flavour-matched to the carbohydrate beverage. It will be consumed within 5 minutes, 30 minutes before exercise.
Fasted control beverage
Other interventionA non-caloric beverage consisting of water and sugar-free flavouring, flavour-matched to the carbohydrate beverage. The beverage will be consumed within 5 minutes following an overnight fast, 30 minutes before exercise.
Treatment groups
24 Participants
are divided into 3 treatment groupsGroup A: Carbohydrate (CHO)Experimental treatment 1 intervention
Group B: Protein (PRO)Experimental treatment 1 intervention
Group C: Fasted (FAST)Placebo comparator 1 intervention
Trial outcomes
Primary outcomes
1
Whole-body carbohydrate oxidation
Whole-body carbohydrate oxidation will be calculated from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during 90 minutes of moderate-intensity cycling. Carbohydrate oxidation will be compared between the carbohydrate, protein, and fasted conditions and between females and males.
Time frame
During the 90-minute exercise bout2
Whole-body fat oxidation
Whole-body fat oxidation will be calculated from VO2 and VCO2 measured by indirect calorimetry during 90 minutes of moderate-intensity cycling. Fat oxidation will be compared between the carbohydrate, protein, and fasted conditions and between females and males.
Time frame
During the 90-min exercise bout3
Exogenous glucose oxidation
Exogenous glucose oxidation will be determined during the carbohydrate condition using breath 13CO2 enrichment following ingestion of \[U-13C6\]-D-glucose. Breath samples will be analyzed by isotope ratio mass spectrometry, and exogenous glucose oxidation will be calculated using 13CO2 enrichment and carbon dioxide production.
Time frame
During the 90-min exercise bout4
Exogenous leucine oxidation
Exogenous leucine oxidation will be determined during the protein condition using breath ¹³CO₂ enrichment following ingestion of L-\[1-¹³C\]leucine. Breath samples will be analyzed by isotope ratio mass spectrometry, and exogenous leucine oxidation will be calculated using breath ¹³CO₂ enrichment and carbon dioxide production.
Time frame
During the 90-min exercise boutSecondary outcomes
1
Time to task failure
Exercise performance will be assessed as time to volitional exhaustion during a cycling time-to-task-failure test performed at 85% of maximal work rate following the 90-minute moderate-intensity cycling bout.
Time frame
Immediately following the 90-min exercise boutSponsors and contacts
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Source ClinicalTrials.gov