How the order of foods in a pre-exercise meal affects fuel use and endurance performance

Effects of Manipulating Food Intake Sequence in the Pre-exercise Meal on Substrate Utilisation and Endurance Performance in Athletes

This trial tests whether eating carbohydrates first or last in a pre-exercise meal changes fuel use and time-trial performance in healthy, trained endurance athletes.

Quick facts

• Phase: Not applicable
• Study type: Interventional
• Enrollment: 19 (estimated)
• Ages: 18 Years to 64 Years
• Sex: Male
• Sponsor: Universidade do Porto (Academic / other)
• Locations: 1 site (Lisbon, Oeiras)
• Trial ID: NCT07503990 on ClinicalTrials.gov

What this trial studies

Researchers will compare two pre-exercise meal patterns—carbohydrate-first versus carbohydrate-last—to see how meal order changes whole-body fat and carbohydrate use at rest and during prolonged exercise at moderate to heavy intensities. Participants are healthy, endurance-trained men who meet performance and training criteria and have normal glucose tolerance. Outcomes include substrate oxidation measures, a time-trial performance test, and metabolic and physiological responses such as blood glucose, lactate, heart rate, ratings of perceived exertion, and appetite. Tests are conducted on-site with controlled meals and exercise protocols to standardize conditions.

Who should consider this trial

Good fit: Ideal candidates are healthy, endurance-trained men aged 18–64 with normal glucose tolerance and the ability to attend on-site testing in Lisbon.

Not a fit: People who are female, not endurance-trained, have impaired glucose metabolism, or take medications that affect glucose or lipid metabolism are unlikely to benefit from participating.

Why it matters

Potential benefit: If successful, the results could give athletes simple, evidence-based meal-order guidance to improve fuel use and endurance performance.

How similar studies have performed: Previous research shows that meal composition and timing can change substrate use and performance, but manipulating the order of foods within a pre-exercise meal is a less-tested, more specific approach.

Eligibility criteria

Inclusion Criteria:

* Adult (18-64 years old)
* Men
* Endurance-trained athletes (meeting training and performance caliber criteria ≥Tier 2; McKay et al., 2022)
* Healthy (meeting the exclusion criteria for medical conditions)
* Normal glucose tolerant according to the latest criteria established by the American Diabetes Association (2024): HbA1c \<5.7%, fasting plasma glucose \<5.6 mmol/L (100 mg/dL) or 2-h plasma glucose \<7.8 mmol/L (140 mg/dL) during a 75-g OGTT
* Able and willing to provide informed consent and safely comply with study procedures

Exclusion Criteria:

* Any medical condition or behaviour deemed either to pose undue personal risk to the participant or introduce bias into the experiment (e.g. cardiovascular disease; alcohol or substance abuse; any condition affecting the glucose or lipid metabolism, reviewed on a case by case basis)
* Any reported medication or supplementation that may interfere with the glucose metabolism (e.g., acarbose, insulin, metformin, semaglutide, thiazolidinediones, sulfonylureas, corticosteroids, thiazide diuretics) or lipid metabolism (e.g., statins, nicotinic acid, colestyramine anhydrous, ezetimibe, fibrates, L-carnitine). Other medication and supplementation will be reviewed on a case by case basis.
* Known food allergy, intolerance or hypersensitivity to any of the test meal ingredients
* Recent change in body mass (± 2 kg in the last 2 months)
* Smoking

Where this trial is running

Lisbon, Oeiras

• Cidade do Futebol — Lisbon, Oeiras, Portugal (Recruiting)

Study contacts

• Principal investigator: Rita Giro — FCNAUP, University of Porto; Federação Portuguesa de Futebol
• Study coordinator: Rita Giro

Conditions Substrate Metabolism; Healthy Participants; Endurance Exercise; food order; meal sequence; glucose metabolism; substrate utilisation; sport nutrition