Does pre-exercise nutrition change sex differences in fuel use during endurance cycling

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

In this randomized, counterbalanced crossover study, 24 recreationally active adults (12 women, 12 men) will complete three trials after different pre-exercise drinks: carbohydrate, protein, or a non-caloric fasted beverage. After an overnight fast and a 30-minute rest, participants cycle at 65% VO2 peak for 90 minutes, followed by a time-to-task-failure test at high intensity. Researchers will measure whole-body carbohydrate and fat oxidation, exogenous substrate use, blood metabolites, and exercise performance to see if pre-exercise nutrition modulates sex-specific fuel utilization. The primary goal is to determine if nutrition before exercise alters sex differences in substrate oxidation; a secondary goal is to evaluate effects on performance. Each participant undergoes all three conditions with washout periods of at least three days.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* 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
* Weight stable, defined as within ±2 kg for at least 6 months
* Non-smoker
* Females must be eumenorrheic

Exclusion Criteria:

* 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

Where it's running

• Goldring Centre for High Performance Sport
  Toronto, Ontario, Canada Recruiting

Study contacts

• Principal investigator: Jenna Gillen, PhD — University of Toronto
• Study coordinator: Jenna Gillen, PhD
• Email: jenna.gillen@utoronto.ca
• Phone: 4169783244

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.